Technical field of the invention
[0001] The present invention refers to a system for automatically moving an articulated
arm, particularly of an articulated crane. The term "articulated arm" means a system
provided with a plurality of bodies, consecutively connected to each other, capable
of forming an open kinematic chain with a plurality of translative and/or rotative
degrees of freedom in the space.
Prior art
[0002] Systems enabling other systems having plural degrees of freedom, to perform previously
stored movements, are known. Such systems provide to manually perform a desired movement,
store it and then automatically re-perform it. Such mode is particularly useful when
identical movements must be cyclically repeated (consider for example the transport
of items from a first area to a second area in a yard, in an industrial area, or similar).
[0003] Overhead cranes are often used in a yard for example. An overhead crane comprises
a U-inverted frame movable along a track (first degree of freedom), and a trolley
transversally movable along the frame (second degree of freedom). Therefore, the absolute
position of the trolley depends on the absolute position of the frame and on the position
of the trolley with reference to the frame. The absolute position of the trolley is
matched by only one configuration of the overhead crane and consequently it can be
simply registered and reproduced a sequence of movements.
[0004] With reference to complex articulated arms, for example in the presence of an articulated
crane, the position of an end-effector of the crane can be obtained by different configurations
of the crane itself. Therefore, simply registering a manual movement and repeating
it do not cause the end-effector to follow the same movements. Indeed, if in the start
position the crane has a configuration different from the one it had in a step of
storing the movement of the end-effector, just simply repeating the movements performed
in the storing step will not enable the end-effector to reach the same stored final
position.
[0005] Systems according to the known art are described in documents
JP 2001 130892 A,
EP 2 725 183 A1,
JP H10 219731 A and
JP 2000 355957 A.
Document
JP 2001 130892 A discloses a system for automatically moving an articulated arm, comprising: said
articulated arm, comprising a plurality of bodies consecutively connected to each
other in order to form an open kinematic chain with an end-effector, having a plurality
of translative and/or rotative degrees of freedom and a plurality of actuators for
moving said bodies; a plurality of sensors associated to said bodies adapted to supply
signals indicative of linear or angular positions such to enable to determine the
(relative) coordinates of the end-effector; a user interface device configured for
commanding the articulated arm by an operator; a control unit comprising a memory
module and operatively connected to said actuators, said sensors and said user interface
device, said control unit being configured for performing: a step of storing a movement
of the end-effector, which comprises: receiving movement instructions of the end-effector
from the user interface device; actuating the actuators so that the end-effector performs
a sequence of movements corresponding to the movement instructions; detecting during
the movement, in a plurality of subsequent sampling instances distanced from each
other of a sampling time, the signals from said sensors; determining, based on the
signals from the sensors, the (relative) coordinates of the end-effector in each sampling
instant; and storing in the memory module the absolute coordinates of the end-effector
determined in each sampling instant and the actuators used for moving the end-effector
between each determined absolute coordinate and the absolute coordinate determined
in the following sampling instant.
Summary of the invention
[0006] Therefore, it is an object of the present invention to provide a system for automatically
moving an articulated arm, particularly of an articulated crane, having a plurality
of degrees of freedom, wherein particularly the same absolute position of the end-effector
can be obtained by plural configurations of the articulated arm itself.
[0007] This and other objects are obtained by a system for automatically moving an articulated
arm according to claim 1.
[0008] The dependent claims define possible advantageous embodiments of the invention.
Brief description of the figures
[0009] For better understanding the invention and appreciating the advantages, some exemplifying
non-limiting embodiments thereof will be described in the following with reference
to the attached figures, wherein:
Figure 1 is a side view of an articulated crane;
Figure 2 is a schematic illustration of an example of the steps of storing the movements
of an articulated arm, based on the invention;
Figure 3 is a schematic illustration of an example of the steps of re-performing the
movements of the articulated arm, based on the invention;
Figure 4 is a schematic illustration of a further example of the steps of re-performing
the movements of the articulated arm, based on the invention;
Figure 5 is a schematic illustration of a further example of the steps of re-performing
the movements of the articulated arm, based on the invention;
Figure 6 is a schematic illustration of a further example of the steps of re-performing
the movements of the articulated arm, based on the invention.
Detailed description of the invention
[0010] The present description will illustratively refer to an articulated crane. However,
the present invention finds an application in the movements of articulated arms of
other types, such as for example robotic arms, or aerial work platforms (PLE).
[0011] Referring to the attached Figure 1, it shows an example of a possible articulated
arm, particularly an articulated crane, for example a hydraulic loading crane (commonly
known as "loader crane"), generally indicated by the reference 101.
[0012] The crane 101 comprises a column 102 pivoting about its axis, and one or more possibly
extendable arms 103', 103". The possibility of extending the arms, if provided, is
obtained by a plurality of extensions 104 reciprocally translatingly movable in order
to modify the axial length of a respective arm. In the example of Figure 1, only the
second arm 103" is extendable by moving the extensions 104. In the following description,
the first arm 103', devoid of extensions, will be indicated by the term "main arm",
while the second arm 103", provided with the extensions 104, will be indicated by
the term "secondary arm". The free end 105 of the last extension of the secondary
arm 103" is commonly known as end-effector. A hook 106 movable for example by a rope
winch 107 can be provided at the end-effector 105.
[0013] For sake of simplicity, it is illustratively assumed the presence of only one extension
104, neglecting the movements of the hooks 106, so that the crane 101 has the following
degrees of freedom:
- 1) rotation of the column 102 about its axis;
- 2) rotation of the main arm 103' with respect to the column 102 about an axis perpendicular
to the plane on which the column 102 and main arm 103' lie;
- 3) rotation of the secondary arm 103" with respect to the main arm 103' about an axis
perpendicular to the plane on which the main arm 103' and secondary arm 103" lie;
- 4) translation of the extension 4 with respect to the secondary arm 103".
[0014] The above described crane therefore provides an open kinematic chain, having a plurality
of sequentially connected bodies (column, main arm, secondary arm, extensions) and
a free end (end-effector).
[0015] The above cited degrees of freedom are matched by the movement of an element of the
articulated arm with respect to another one (degrees of freedom 2, 3, 4) or with respect
to a reference (degree of freedom 1). In order to perform such movements, the crane
101 comprises a plurality of actuators, at least one actuator corresponding to a specific
degree of freedom. With reference to Figure 1, a first hydraulic jack 108, moving
the main arm 103' with respect to the column 102, a second hydraulic jack 109, moving
the secondary arm 103" with respect to the main arm 103', and an actuator 110 moving
the column 102 with respect to a stationary reference, are shown. Obviously, further
actuators (not shown in the figures), for example of a hydraulic-type, for moving
the extensions 104, are present. Obviously, even though the actuators of the cranes
are normally of a hydraulic-type, generally it is possible to provide actuators of
a different kind (electric or pneumatic, for example) in the articulated arms.
[0016] The crane 101 comprises a plurality of sensors capable of enabling to determine the
absolute coordinates of the end-effector 105, particularly the Cartesian coordinates
thereof. For example, it is assumed that the origin of a Cartesian coordinate system,
coincides with the base of the column 102, so that the absolute coordinates of the
end-effector 105 are expressable by three values: x, y, z.
[0017] According to a possible embodiment, with reference to the crane 101, the plurality
of sensors can include, for example:
- 1) an angular sensor for measuring the rotation of the column 102 about its axis;
- 2) an angular sensor for measuring the rotation of the main arm 103'. This measured
rotation can be absolute, in other words referred to a stationary reference such as
the horizontal, or can be a relative rotation, with respect to the column 102;
- 3) an angular sensor for measuring the rotation of the secondary arm 103". This measured
rotation can be absolute, in other words referred to a stationary reference such as
the horizontal, or can be a relative rotation, with respect to the main arm 103';
- 4) a linear sensor for measuring the translation of the extension 104 with reference
to the secondary arm 103".
[0018] For example, the sensors can include linear or angular encoders, inclinome-ters,
magnetostrictive position sensors or similar. From the signals output by the above
cited sensors, it is possible to determine, by geometrical relationships, the absolute
coordinates of the end-effector 105.
[0019] The crane 101 comprises a control unit operatively connected to the actuators, for
moving them, and to the sensors, for receiving signals indicative of the above cited
magnitudes. Moreover, the control unit comprises a memory module, the operation thereof
will be explained in the following.
[0020] In addition, it is provided a user interface device connected to the control unit
for enabling an operator to manually move the crane and, possibly, to gain access
to other functions. For example, the user interface device can comprise a remote control
and the control unit can comprise a transmission module for communicating with this
latter (a radio transmission module, for example). The operator, by acting on a joystick
of the remote control for example, can visually move the end-effector 105 among subsequent
positions. As said in the introductory part, since a position of the end-effector
105 can generally correspond to more than one configuration of the crane, also the
movements of the end-effector 105 can be performed in different ways, in other words
by sequentially moving several actuators. Consequently, predefined operative logics
are generally provided, by which, based on a desired determined movement of the end-effector,
corresponding actuators are selected to be operated for obtaining this movement.
[0021] Therefore, the control unit is configured so that, upon a movement instruction of
the end-effector received from the user interface device, such movement is obtained
as a function of a predetermined logic for actuating the actuators. For example, the
actuating logics can be one for minimizing the oil flow rate required for actuating
the actuators or can be one for minimizing the energy used for moving them. A further
logic can be one of the minimum distance travelled by the end-effector for reaching
the desired position. A further criterion. often used for example in combination with
one of the above listed ones, consists of maintaining the actuators away from the
stop position. The predetermined operative logics are per se known and therefore will
not be specifically described.
[0022] Alternatively, the operator can decide which actuators to move: only one or more
than one at a time, and consequently can obtain the desired movement of the end-effector.
[0023] By a system configured in this way, it is possible to store a sequence of movements
manually imparted by the user interface device, and then automatically repeat the
same by modes which will be described in the following.
[0024] The control unit is particularly configured to perform a step of storing a movement
of the end-effector 105, comprising:
- receiving instructions of moving the end-effector 105 by the user interface device;
- actuating the actuators so that the end-effector 105 performs a sequence of movements
corresponding to the movement instructions. The actuators can be moved based on a
predetermined logic (for example for minimizing the flow rate or minimum travelled
distance), or the operator himself/herself directly moves certain actuators, by the
user interface device, so that the end-effector 105 performs determined movements
in the space;
- sensing, during the movement, at a plurality of consecutive sampling instants spaced
from each other by a sampling time, the signals from the sensors. The sampling time
can be predefined or alternatively can be set by the operator. Preferably, the sampling
time is less than one second, still more preferably is in the order of a one tenth
of a second;
- determining the absolute coordinates of the end-effector 105 at each sampling instant
based on the signals from the sensors;
- storing in the memory module the absolute coordinates of the end-effector 105 determined
at each sampling instant, and the actuators used for moving the end-effector 105 between
each determined absolute coordinate and the absolute coordinate determined at the
following sampling instant. It is observed that, in this step, with reference to the
signals from the sensors, just the absolute coordinates of the end-effector are stored,
and it is not required to store the configuration of the crane, also obtainable from
the signals of the sensors. Moreover, with reference to the actuators, the memory
stores only the used actuators, and it is not required to store neither the movement
direction, nor the (angular or linear) travelled distance of the actuators themselves.
[0025] Consequently, the real trajectory followed by the end-effector 105, based on the
manual instructions of the operator, is divided in a plurality of discrete points,
each corresponding to a sampling instant, and further the actuators used in the trajectory
segments defined by said following points, are stored.
[0026] Based on such stored information, therefore the control unit can act on the actuators
in order to re-perform the stored movement, particularly by automatically moving the
crane in the following way.
[0027] Particularly, the command unit is configured to implement a step of re-performing
the movement stored upon an instruction of automatically re-performing the stored
movement. For example, such step can be started by the operator by the user interface
device.
[0028] Such step of re-performing the stored movement provides to divide the re-performing
step into a plurality of partial re-performing periods, each delimited by two consecutive
re-performing instants distanced by a re-performing partial time, which, according
to a possible embodiment, is equal to the sampling time. Alternatively, the partial
re-performing time could be different from the sampling time (it could be selectable
by the operator, for example) and in this case the duration of the re-performing step
will be different from the duration of the storing step. The re-performing step comprises,
during each partial re-performing period:
- sensing, at the initial re-performing instant, the signals from the sensors;
- determining the effective absolute coordinates of the end-effector 105 and the configuration
of the articulated arm based on the signals from the sensors. It is observed that,
as opposed to the storing step, the step of re-performing the configuration of the
articulated arm, is monitored. For example, with reference to Figure 1, it is possible
to determine if the secondary arm 103" and main arm 103' are aligned to each other
or if they form a determined relative angle;
- comparing the effective absolute coordinates of the end-effector 105 with the absolute
coordinates of the end-effector 105 stored in each of the sampling instant. Preferably,
such step is performed with a determined tolerance, in other words the effective absolute
coordinates are considered equal to the stored absolute coordinates if the effective
absolute coordinates are equal to the stored absolute coordinates plus or minus a
determined dimensional tolerance;
- if the effective absolute coordinates of the end-effector 105 are equal (preferably
plus or minus the above given tolerance) to one of the absolute coordinates of the
end-effector stored during one of the sampling instants, actuating the stored actuators
for moving the end-effector 105 towards the absolute coordinate stored at the following
sampling instant. If the crane has the same configuration which it had in the corresponding
position of the end-effector during the storing step, this passage is sufficient to
reach the absolute coordinate stored at the following sampling instant;
- if it is determined based on the configuration of the crane that the end-effector
105 is not capable of reaching the absolute coordinate stored at the following sampling
instant, preferably further actuating one or more additional actuators according to
a predetermined operative logic. Such condition can also happen if, despite the absolute
coordinate corresponds to the stored one, the crane has a different configuration.
In this case, further movements will be required for reaching the absolute coordinate
stored at the following sampling instant.
[0029] On the contrary, if the effective absolute coordinates of the end-effector 105 are
not equal to one of the absolute coordinates of the end-effector, stored at one of
the sampling instants, two different conditions can occur: the end-effector 105 lies
along the stored trajectory, or the end-effector 105 lies outside the stored trajectory.
Advantageously, the control unit is therefore configured to:
- determine the whole stored trajectory of the end-effector. This can be obtained for
example as a polygonal chain joining the different stored absolute coordinates of
the end-effector or by a (polynomial for example) interpolation of the same.
- If the effective absolute coordinate of the end-effector 105 lies in a segment of
the trajectory comprised between a first and second absolute coordinates stored between
two following sampling instants, actuate the stored actuators for moving the end-effector
105 between said two absolute coordinates stored between two following sampling instants;
- if the end-effector 105 is determined as not capable of reaching the second stored
absolute coordinate based on the configuration of the crane, actuate one or more additional
actuators according to a predetermined operative logic.
[0030] If the effective absolute coordinate of the end-effector 105 lies outside the stored
trajectory, advantageously the control unit is configured to:
- calculate the point of the stored trajectory nearest to the effective absolute coordinate
of the end-effector;
- actuate the actuators according to a predetermined operative logic for moving the
end-effector to such point. Such nearest point can be both a beforehand stored point,
and a not stored point being anyway comprised between two following stored points.
According to one of the two conditions, it is therefore implemented one of the abovementioned
modes.
[0031] Advantageously, the movements of the end-effector 105 between two following points,
for example between two points whose absolute coordinates were stored, are performed
preferably by a closed-loop control of the position of the end-effector (according
to the logics P, PI, PD, PI, PID, for example), wherein the reference is the trajectory
of the end-effector. For example, if the two desired end points are known, the reference
trajectory between these points can be set equal to the segment joining such points.
[0032] From what discussed above it is assumed that the movement is re-performed during
the same time used for the storing step.
[0033] However, it is also possible to re-perform the stored trajectory at a different speed,
in other words so that the end-effector performs such stored trajectory in a re-performing
total time greater or less than the total stored time (given by the summation of the
sampling times).
[0034] Therefore, the control unit is advantageously configured to receive, as an input
parameter, a total desired re-performing time. Such parameter can be supplied to the
control unit by the user interface device, for example.
[0035] Particularly, the control unit is configured to:
- determine the stored trajectory of the end-effector. This step can be performed according
to what was previously discussed;
- calculate on the stored trajectory, the equivalent absolute coordinates of the end-effector,
corresponding to the absolute coordinates of the end-effector which were sensed during
the movement storing step if the end-effector had performed the estimated trajectory
in the desired re-performing total time;
- set the stored absolute coordinates of the end-effector equal to said equivalent absolute
coordinates.
[0036] Consequently, the stored coordinates are effectively manipulated so that they are
substituted with new equivalent coordinates which take into account that the movement
re-performing step is done at a speed different from the speed of the storing step.
[0037] At this point, it is required to distinguish the case wherein the desired speed during
the performing step is greater or less than the speed of the storing step.
[0038] Advantageously, the control unit is configured to:
- if the total desired re-performing time is greater than the total sampling time (in
other words, if it is desired to decrease the performing speed), store, for each equivalent
absolute coordinate, the actuators stored in the segment of the trajectory along which
the equivalent absolute coordinate lies. Consequently, each equivalent absolute coordinate
is matched by the actuators to be used (if the crane configuration enables that) during
the re-performing step, which are the same ones stored for the trajectory segment
along which the equivalent absolute coordinates lie. Therefore, it is possible to
implement what was previously described;
- if the total desired performing time is less than the total sampling time (in other
words if it is desired to increase the speed), store for each equivalent absolute
coordinate the actuators used along the segment of the trajectory along which the
equivalent absolute coordinate lies and along all the previous segments. In other
words, since the speed increases, between two following equivalent absolute coordinates,
additional segments of the stored trajectory can be included. So, the actuators stored
for each equivalent absolute coordinate will be those stored for all the segments
included between it and the previous equivalent absolute coordinate. Then, again,
the following will be the same as previously described.
[0039] Some operative examples will be given for further explaining what was hereinbefore
discussed.
[0040] Figure 2 illustrates the steps of storing a possible trajectory of an articulated
arm. Particularly, the figure schematically shows the articulated arm having the column
102, the main arm 103', the secondary arm 103", and a single extension 104, terminating
with the end-effector 105. The initial position of the end-effector 105 is indicated
by the coordinates x1, y1, z1. The stored movements are the following:
- the elapse of the sampling time, from the position x1, y1, z1 (initial position) to
the position x2, y2, z2. The absolute coordinates of both positions are stored. Based
on the predetermined operative logic, for example, consisting of minimizing the oil
flow rate, or based on a decision of the operator, the second position is reached
by projecting the extension 104, which entails the actuation of a corresponding actuator,
which is also stored (therefore Figure 2 shows, besides x1, y1, z1 and x2, y2, z2,
also the reference 104 for indicating that during this elapse the extension 104 were
moved). Storing the configuration of the arm is not required. For example, storing
the angle included between the main arm 103' and secondary arm 103" is not required.
Neither storing the direction and length of the movement of the actuator moving the
extension 104 are required;
- the elapse of the sampling time from the second position x2, y2, z2 to the third position
x3, y3, z3 which is stored. According to the example, the third position is reached
by rotating the secondary arm 103" and by a further projection of the extension 104.
Using two corresponding actuators of the secondary arm 103" and extension 104 is also
stored.
[0041] Now it is made reference to the re-performing step, if the initial position of the
end-effector corresponds to the stored initial position x1, y1, z1, if the initial
configuration of the crane is the same as the one the crane had during the step of
storing the position x1, y1, z1 and if the desired performing speed is as the speed
used in the storing step, the crane will exactly perform the same movements by actuating
the same actuators used in the different segments of the trajectory of the storing
step, according to what was shown in Figure 2. Checking the configuration performed
at the point x1, y1, z1 will confirm that the only projection of the extension 104
enables to reach the coordinate x2, y2, z2.
[0042] Referring now to Figure 3, if it were tried to follow again a stored trajectory by
simply actuating the same actuators used in the different segments of the trajectory
of a storing step (in other words only the actuator of the extension 104) in a case
wherein the initial position of the end-effector corresponds to the stored initial
position x1, y1, z1, but the initial configuration of the crane is not the same as
the one the crane had in the storing step in the position x1, y1, z1, the end-effector
105 would not be able to reach the stored position x2, y2, z2 because a rotation is
also required. Therefore the control unit, once it verifies by the signals of the
sensor that the only stored actuators do not enable to reach the position x2, y2,
z2 based for example on the minimum flow rate logic, actuates also actuates also the
actuators which moves the secondary arm 103" so that the end-effector 105 effectively
reaches the position x2, y2, z2. Then, even though the effective configuration of
the crane in the position x2, y2, z2 is not exactly the same as the stored one, the
control unit checks that, in the configuration of the coordinate x2, y2, z2, the end-effector
105 is anyway capable to move to the position x3, y3, z3 by actuating only the stored
actuators between the coordinates x2, y2, z2 and x3, y3, z3, in other words the actuators
moving the secondary arm 103" and extension 104. These latter perform movements which
are slightly different from the stored ones. From this example, it is observed that,
even though the initial configuration of the crane is different from the one it had
in the storing step, as the stored movement is gradually re-performed, the articulated
arm tends to approach to the corresponding configuration it had in the storing step.
[0043] Referring now to Figure 4, if the initial position of the end-effector 105 does not
correspond to the stored initial position x1, y1, z1, the control unit moves the end-effector
105, for example according to the minimum flow rate logic, so that this moves to the
nearest point along the stored trajectory, a point which does not necessarily coincide
with a stored point. In the example, such point, indicated by X, is in the segment
between the coordinates x1, y1, z1 and x2, y2, z2. Therefore, the control unit, during
the partial re-performing time, will move the end-effector 105 to such nearest point
in the stored trajectory and, after that, it tries to move the end-effector to the
point of coordinates x2, y2, z2 by actuating only the actuator moving the extension
104 (which was the stored actuator for moving from coordinates x1, y1, z1 to coordinates
x1, y1, z1), however, since is not capable of doing it, it will actuates also a second
actuator, in this case the actuator moving the secondary arm 103", according to the
predetermined set logic. Then, the step of re-performing the movement continues according
to what was discussed with reference to Figure 3. Obviously, if the effective sensed
initial point does not coincide with a stored point, but was already present in the
trajectory, the end-effector 105 would not be required to be moved to the nearest
point of the trajectory since the end-effector is already present in the trajectory.
[0044] With reference now to Figure 5, it is described the case wherein the re-performing
step is executed with a speed different from the speed used during the storing step.
For the sake of simplicity, it is considered the case wherein the initial position
of the end-effector corresponds to the stored initial position x1, y1, z1 and wherein
the initial configuration of the crane is the same as the one the crane had during
the step of storing the position x1, y1, z1.
[0045] For example, if it is desired to halve the performing speed, the total re-performing
desired time is twice the total sampling time. Therefore, if it is considered, for
example, the segment between the coordinates x1, y1, z1 and x2, y2, z2, and the time
the crane requires, during the storing step, to move between these two positions (such
time being equal to the sampling time), during the re-performing step, the end-effector
could reach only a position x12 intermediate between x1 and x2, which represents an
equivalent absolute coordinate. Therefore, the control unit will actuate the same
actuator used in the storing step for moving from position x1, y1, z1 to position
x2, y2, z2, in other words the one moving the extension 104 which, due to the sensed
configuration of the crane, enables to reach the position x2, y2, z2 without actuating
other actuators. Then, it is followed the same logic along all the trajectory.
[0046] Referring now to Figure 6, if, on the other hand, it is desired to increase the performing
speed, the total desired performing time is reduced with respect to the total sampling
time during the storing step. Consequently, for example, during the time required
to the crane, in the storing step, to move from coordinates x1, y1, z1 to x2, y2,
z2, in the re-performing step, the end-effector 105 could simultaneously reach, for
example, a position x23 intermediate between x2 and x3, which is an equivalent performing
coordinate. Therefore, by means of the position x1, y1, z1, the control unit will
actuate the same actuators used in the storing step for moving between the positions
x1, y1, z1 and x2, y2, z2, and between the positions x2, y2, z2 and x3, y3, z3, in
other words the actuators which move the extension 104 and the actuator which moves
the secondary arm 103". If the point x23 is not reached by means of these actuators
due to the sensed configuration, the control unit would further actuate one or more
other actuators according to the predetermined operative logic.
[0047] In the present description and in the attached claims, it is observed that the control
unit and also the elements indicated by the expression "module", could be implemented
by hardware devices (central units, for example), by software or by a combination
of hardware and software.
[0048] From the above given description, a person skilled in the art could appreciate that
the system, according to the invention, enables to re-perform stored movements also
in the presence of complicated articulated arms, wherein the same position of the
end-effector is obtainable by different configurations of the arm itself.
1. System for automatically moving an articulated arm (101), comprising:
- said articulated arm (101), comprising a plurality of bodies consecutively connected
to each other in order to form an open kinematic chain with an end-effector (105),
having a plurality of translative and/or rotative degrees of freedom and a plurality
of actuators for moving said bodies;
- a plurality of sensors associated to said bodies adapted to supply signals indicative
of linear or angular positions such to enable to determine absolute coordinates of
the end-effector (105);
- a user interface device configured for commanding the articulated arm by an operator;
- a control unit comprising a memory module and operatively connected to said actuators,
said sensors and said user interface device, said control unit being configured for
performing:
a step of storing a movement of the end-effector (105), which comprises:
- receiving movement instructions of the end-effector (105) from the user interface
device;
- actuating the actuators so that the end-effector (105) performs a sequence of movements
corresponding to the movement instructions;
- detecting during the movement, in a plurality of subsequent sampling instances distanced
from each other of a sampling time, the signals from said sensors;
- determining, based on the signals from the sensors, the absolute coordinates of
the end-effector (105) in each sampling instant;
- storing in the memory module the absolute coordinates of the end-effector (105)
determined in each sampling instant and the actuators used for moving the end-effector
(105) between each determined absolute coordinate and the absolute coordinate determined
in the following sampling instant;
a step of re-performing the movement of the end-effector (105) stored in the storing
step upon an instruction of automatically re-performing the stored movement, comprising,
in a plurality of partial re-performing periods, each delimited by two subsequent
performing instants spaced by a partial re-performing time:
- detecting, at the starting re-performing instant of each partial re-performing period,
the signals from the sensors;
- determining the effective absolute coordinates of the end-effector (105) and the
configuration of the articulated arm based on said signals from the sensors;
- comparing the effective absolute coordinates of the end-effector (105) with the
absolute coordinates of the end-effector (105) stored in each of the sampling instants;
- if the effective absolute coordinates of the end-effector (105) are the same as
one of the absolute coordinates of the end-effector, stored in one of the sampling
instants, actuating the stored actuators for performing the movement of the end-effector
towards the absolute coordinate stored at the following sampling instant.
2. System according to claim 1, wherein said step of re-performing the movement of the
end-effector (105) further comprises:
- if it is determined, based on the configuration of the articulated arm, that the
end-effector (105) is not capable of reaching the absolute coordinate stored at the
following sampling instant, further actuating one or more additional actuators according
to a predetermined operative logic.
3. System according to claim 1 or 2, wherein said step of storing in the memory module
the absolute coordinates of the end-effector (105) is performed without storing the
configuration of the articulated arm obtainable by the signals from said sensors.
4. System according to anyone of the preceding claims, wherein said step of storing in
the memory module the actuators used for moving the end-effector (105) is performed
without storing the movement directions and extents of the movements of the actuators.
5. System according to any of the preceding claims, wherein said step of comparing the
effective absolute coordinates of the end-effector (105) with the absolute coordinates
of the end-effector (105) stored in each of the sampling instants is performed with
a predefined tolerance.
6. System according to any of the preceding claims, wherein said step of re-performing
the movement of the end-effector (105) further comprises, if the effective absolute
coordinates of the end-effector (105) are not the same as one of the absolute coordinates
of the end-effector stored in one of the sampling instants:
- determining the overall stored trajectory of the end-effector (105);
- if the effective absolute coordinate of the end-effector (105) lies in a segment
of the trajectory comprised between a first and second stored absolute coordinates
between two following sampling instants, actuating the stored actuators for performing
the movement of the end-effector (105) between said two stored absolute coordinates
between two following sampling instants;
- if it is determined, based on the configuration of the articulated arm, that the
end-effector (105) is not capable of reaching the second stored absolute coordinate,
actuating one or more further actuators according to a predetermined operative logic.
7. System according to the preceding claim, wherein said step of re-performing the movement
of the end-effector (105) further comprises, if the effective absolute coordinate
of the end-effector (105) lies outside the stored trajectory:
- calculating the point of the stored trajectory, nearest to the effective absolute
coordinate of the end-effector (105);
- actuating the actuators according to a predetermined logic for moving the end-effector
(105) to said point.
8. System according to any of the preceding claims, wherein the partial re-performing
time is equal to the sampling time.
9. System according to any of the preceding claims, wherein the control unit is configured
for receiving as an input parameter a desired overall re-performing time, wherein
said step of re-performing the movement of the end-effector (105), if the desired
overall re-performing time is different from the overall time for moving the end-effector
during the storing step, comprises:
- determining the stored trajectory of the end-effector (105);
- calculating, on the stored trajectory, equivalent absolute coordinates of the end-effector,
corresponding to the absolute coordinates of the end-effector which would be detected
in the step of storing the movement if the end-effector had performed the determined
trajectory in the desired overall re-performing time;
- setting the absolute stored coordinates of the end-effector equal to said equivalent
absolute coordinates.
10. System according to the preceding claim, wherein said step of re-performing the movement
of the end-effector (105) further comprises:
- if the overall desired re-performing time is greater than the overall time of moving
the end-effector during the storing step, storing for each equivalent absolute coordinate
the stored actuators along the segment of the trajectory on which lies the equivalent
absolute coordinate;
- if the overall desired performing time is less than the overall time of moving the
end-effector during the storing step, storing for each equivalent absolute coordinate
the actuators used in the segment of the trajectory on which lies the equivalent absolute
coordinate and in all the previous segments.
11. System according to any of the preceding claims, wherein said control unit is configured
for performing a closed-loop control of the trajectory between a first absolute coordinate
and a second absolute coordinate of the end-effector (105).
12. System according to any of the preceding claims, wherein said absolute coordinates
of the end-effector (105) are absolute cartesian coordinates in a 3D space.
13. System according to any of the preceding claims, wherein said articulated arm (101)
comprises an articulated crane.
14. System according to the preceding claim, wherein said articulated crane comprises
a column (102) rotating around the axis thereof, a main arm (103') rotating around
the column (102), a secondary arm (103") rotating around the main arm (103') and comprising
at least an extension translatingly extendable from the secondary arm itself, and
said plurality of sensors comprises an angular sensor for measuring the rotation of
the column (102) around the axis thereof, an angular sensor for measuring the rotation
of the main arm (103'), an angular sensor for measuring the rotation of the secondary
arm (103"), a linear sensor for measuring the translation of the extension (104) from
the secondary arm (103").
1. System zum automatischen Bewegen eines Gelenkarmes (101), umfassend:
- den Gelenkarm (101), umfassend mehrere Körper, die aufeinanderfolgend miteinander
verbunden sind, um eine offene kinematische Kette mit einem Endeffektor (105) zu bilden,
der mehrere translatorische und/oder rotatorische Freiheitsgrade und mehrere Aktuatoren
zum Bewegen der Körper aufweist;
- mehrere Sensoren, die den genannten Körpern zugeordnet sind und Signale liefern
können, die lineare Positionen oder Winkelpositionen anzeigen, so dass die absoluten
Koordinaten des Endeffektors (105) bestimmt werden können;
- eine Benutzerschnittstellenvorrichtung, die zur Steuerung des Gelenkarms durch einen
Bediener konfiguriert ist;
- eine Steuereinheit, die ein Speichermodul umfasst und mit den Aktuatoren, den Sensoren
und der Benutzerschnittstellenvorrichtung operativ verbunden ist, wobei die Steuereinheit
für die Durchführung der folgenden Aufgaben konfiguriert ist:
ein Schritt zum Speichern einer Bewegung des Endeffektors (105), Folgendes umfassend:
- Empfangen von Bewegungsanweisungen des Endeffektors (105) von der Benutzersch nittstellenvorrichtu
ng;
- Betätigen der Aktuatoren, so dass der Endeffektor (105) eine Bewegungssequenz ausführt,
die den Bewegungsanweisungen entspricht;
- Erfassen der Signale von den Sensoren, während der Bewegung, in mehreren aufeinanderfolgenden,
voneinander beabstandeten Abtastzeitpunkten;
- Bestimmen, anhand der Signale der Sensoren, der absoluten Koordinaten des Endeffektors
(105) in jedem Abtastzeitpunkt;
- Speichern, im Speichermodul, der absoluten Koordinaten des Endeffektors (105), die
in jedem Abtastzeitpunkt bestimmt wurden, sowie der Aktuatoren, die zum Bewegen des
Endeffektors (105) zwischen jeder bestimmten absoluten Koordinate und der im folgenden
Abtastzeitpunkt bestimmten absoluten Koordinate verwendet werden;
ein Schritt des Wiederausführens der Bewegung des Endeffektors (105), der in dem Speicherschritt
gespeichert wurde, und zwar auf eine Anweisung zum automatischen Wiederausführen der
gespeicherten Bewegung hin, und in mehreren Teilwiederausführungsperioden, die jeweils
durch zwei aufeinanderfolgende Ausführungszeitpunkte begrenzt sind, die durch eine
Teilwiederausführungszeit beabstandet sind, Folgendes umfassend:
- Erfassen der Signale von den Sensoren im Wiederausführungszeitpunkt des Beginns
jeder Teilwiederausführungsperiode;
- Bestimmen der effektiven absoluten Koordinaten des Endeffektors (105) und der Konfiguration
des Gelenkarms auf der Grundlage der genannten Signale von den Sensoren;
- Vergleichen der effektiven absoluten Koordinaten des Endeffektors (105) mit den
in jedem der Abtastzeitpunkte gespeicherten absoluten Koordinaten des Endeffektors
(105);
- wenn die effektiven absoluten Koordinaten des Endeffektors (105) mit einer der absoluten
Koordinaten des Endeffektors, die in einem der Abtastzeitpunkte gespeichert sind,
übereinstimmen, Betätigen der gespeicherten Aktuatoren zur Durchführung der Bewegung
des Endeffektors in Richtung der im folgenden Abtastzeitpunkt gespeicherten absoluten
Koordinate.
2. System nach Anspruch 1, wobei der Schritt des Wiederausführens der Bewegung des Endeffektors
(105) weiterhin Folgendes umfasst:
- wenn auf der Grundlage der Konfiguration des Gelenkarms festgestellt wird, dass
der Endeffektor (105) nicht in der Lage ist, die im folgenden Abtastzeitpunkt gespeicherte
absolute Koordinate zu erreichen, weiteres Betätigen eines oder mehrerer zusätzlicher
Aktuatoren nach einer vorgegebenen operativen Logik.
3. System nach Anspruch 1 oder 2, wobei der Schritt des Speicherns der absoluten Koordinaten
des Endeffektors (105) in dem Speichermodul ohne Speicherung der Konfiguration des
Gelenkarms durchgeführt wird, die durch die Signale der Sensoren erhalten werden kann.
4. System nach einem der vorhergehenden Ansprüche, wobei der Schritt des Speicherns der
für die Bewegung des Endeffektors (105) verwendeten Aktuatoren in dem Speichermodul
durchgeführt wird, ohne die Richtungen und Ausmaße der Bewegungen der Aktuatoren zu
speichern.
5. System nach einem der vorhergehenden Ansprüche, wobei der Schritt des Vergleichens
der effektiven absoluten Koordinaten des Endeffektors (105) mit den absoluten Koordinaten
des Endeffektors (105), die in jedem der Abtastzeitpunkte gespeichert sind, mit einer
vordefinierten Toleranz durchgeführt wird.
6. System nach einem der vorhergehenden Ansprüche, wobei der Schritt des Wiederausführens
der Bewegung des Endeffektors (105), wenn die effektiven absoluten Koordinaten des
Endeffektors (105) nicht mit einer der absoluten Koordinaten des Endeffektors übereinstimmen,
die in einem der Abtastzeitpunkte gespeichert wurden, Folgendes umfasst:
- Bestimmen der gesamten gespeicherten Bahn des Endeffektors (105);
- wenn die effektive absolute Koordinate des Endeffektors (105) in einem Segment der
Bahn liegt, das zwischen einer ersten und einer zweiten gespeicherten absoluten Koordinate
zwischen zwei folgenden Abtastzeitpunkten liegt, Betätigen der gespeicherten Aktuatoren
zur Durchführung der Bewegung des Endeffektors (105) zwischen den beiden gespeicherten
absoluten Koordinaten zwischen zwei folgenden Abtastzeitpunkten;
- wenn aufgrund der Konfiguration des Gelenkarms festgestellt wird, dass der Endeffektor
(105) nicht in der Lage ist, die zweite gespeicherte absolute Koordinate zu erreichen,
Betätigen eines oder mehrerer weiterer Aktuatoren nach einer vorgegebenen operativen
Logik.
7. System nach dem vorhergehenden Anspruch, wobei der Schritt des Wiederausführens der
Bewegung des Endeffektors (105), wenn die effektive absolute Koordinate des Endeffektors
(105) außerhalb der gespeicherten Bahn liegt, ferner Folgendes umfasst:
- Berechnen des Punktes der gespeicherten Bahn, der der effektiven absoluten Koordinate
des Endeffektors (105) am nächsten liegt;
- Betätigen der Aktuatoren nach einer vorgegebenen Logik, um den Endeffektor (105)
zu diesem Punkt zu bewegen.
8. System nach einem der vorhergehenden Ansprüche, wobei die Teilwiederausführungszeit
gleich der Abtastzeit ist.
9. System nach einem der vorhergehenden Ansprüche, wobei die Steuereinheit so konfiguriert
ist, dass sie als Eingangsparameter eine gewünschte Gesamtwiederausführungszeit empfängt,
wobei der Schritt des Wiederausführens der Bewegung des Endeffektors (105), wenn sich
die gewünschte Gesamtwiederausführungszeit von der Gesamtzeit für die Bewegung des
Endeffektors während des Speicherschritts unterscheidet, Folgendes umfasst:
- Bestimmen der gespeicherten Bahn des Endeffektors (105);
- Berechnen, auf der gespeicherten Bahn, von äquivalenten absoluten Koordinaten des
Endeffektors, die den absoluten Koordinaten des Endeffektors entsprechen, die im Schritt
der Speicherung der Bewegung erkannt würden, wenn der Endeffektor die bestimmte Bahn
in der gewünschten Gesamtwiederausführungszeit ausgeführt hätte;
- Einstellen der absoluten gespeicherten Koordinaten des Endeffektors gleich den genannten
äquivalenten absoluten Koordinaten.
10. System nach dem vorhergehenden Anspruch, wobei der Schritt des Wiederausführens der
Bewegung des Endeffektors (105) weiterhin Folgendes umfasst:
- wenn die gewünschte Gesamtwiederausführungszeit größer als die Gesamtzeit der Bewegung
des Endeffektors während des Speicherschritts ist, Speichern der gespeicherten Aktuatoren
für jede äquivalente absolute Koordinate entlang des Segments der Bahn, auf dem die
äquivalente absolute Koordinate liegt;
- wenn die gewünschte Gesamtwiederausführungszeit kürzer als die Gesamtzeit der Bewegung
des Endeffektors während des Speicherschritts ist, Speichern, für jede äquivalente
absolute Koordinate, der Aktuatoren, die in dem Segment der Bahn, auf dem die äquivalente
absolute Koordinate liegt, und in allen vorhergehenden Segmenten verwendet wurden.
11. System nach einem der vorhergehenden Ansprüche, wobei die Steuereinheit so konfiguriert
ist, dass sie eine Regelung der Bahn zwischen einer ersten absoluten Koordinate und
einer zweiten absoluten Koordinate des Endeffektors (105) durchführt.
12. System nach einem der vorhergehenden Ansprüche, wobei die absoluten Koordinaten des
Endeffektors (105) absolute kartesische Koordinaten in einem dreidimensionalen Raum
sind.
13. System nach einem der vorhergehenden Ansprüche, wobei der Gelenkarm (101) einen Gelenkkran
umfasst.
14. System nach dem vorhergehenden Anspruch, wobei der Gelenkkran Folgendes umfasst:
eine Säule (102), die sich um ihre Achse dreht, einen Hauptarm (103'), der sich um
die Säule (102) dreht, einen Sekundärarm (103"), der sich um den Hauptarm (103') dreht
und mindestens eine Verlängerung umfasst, die von dem Sekundärarm selbst translativ
ausfahrbar ist, und
wobei die mehreren Sensoren Folgendes umfassen: einen Winkelsensor zum Messen der
Drehung der Säule (102) um ihre Achse, einen Winkelsensor zum Messen der Drehung des
Hauptarms (103'), einen Winkelsensor zum Messen der Drehung des Sekundärarms (103"),
einen Linearsensor zum Messen der Verschiebung der Verlängerung (104) von dem Sekundärarm
(103").
1. Système de déplacement automatique d'un bras articulé (101), comprenant :
- ledit bras articulé (101) comprenant une pluralité de corps reliés de manière consécutive
pour former une chaîne cinématique ouverte avec un effecteur terminal (105), présentant
une pluralité de degrés de liberté en translation et/ou en rotation et une pluralité
d'actionneurs permettant de déplacer lesdits corps ;
- une pluralité de capteurs associés auxdits corps, conçus pour fournir des signaux
indiquant des positions linéaires ou angulaires de manière à permettre de déterminer
les coordonnées absolues de l'effecteur terminal (105) ;
- un dispositif d'interface utilisateur configuré pour commander le bras articulé
du fait d'un opérateur ;
- une unité de commande comprenant un module de mémoire et reliée de manière fonctionnelle
auxdits actionneurs, auxdits capteurs et audit dispositif d'interface utilisateur,
ladite unité de commande étant configurée pour réaliser :
une étape de stockage d'un déplacement de l'effecteur terminal (105), qui comprend
:
- la réception des instructions de déplacement de l'effecteur terminal (105) du dispositif
d'interface utilisateur ;
- l'actionnement des actionneurs pour que l'effecteur terminal (105) effectue une
séquence de déplacements correspondant aux instructions de déplacement ;
- la détection pendant le déplacement, dans une pluralité d'instances d'échantillonnage
ultérieures éloignées les unes des autres d'un temps d'échantillonnage, des signaux
provenant desdits capteurs ;
- la détermination, à partir des signaux provenant des capteurs, des coordonnées absolues
de l'effecteur terminal (105) à chaque instant d'échantillonnage ;
- le stockage dans le module de mémoire des coordonnées absolues de l'effecteur terminal
(105) déterminées à chaque instant d'échantillonnage et des actionneurs utilisés pour
déplacer l'effecteur terminal (105) entre chaque coordonnée absolue déterminée et
la coordonnée absolue déterminée dans l'instant d'échantillonnage suivant ;
une étape de réexécution du déplacement de l'effecteur terminal (105) stocké à l'étape
de stockage sur une instruction de réexécution automatique du déplacement stocké,
comprenant, dans une pluralité de périodes de réexécution partielles, chacune étant
délimitée par deux instants d'exécution ultérieurs espacés par un temps de réexécution
partiel :
- la détection, à l'instant de réexécution de départ de chaque période de réexécution
partielle, des signaux provenant des capteurs ;
- la détermination des coordonnées absolues effectives de l'effecteur terminal (105)
et la configuration du bras articulé en fonction desdits signaux provenant des capteurs
;
- la comparaison des coordonnées absolues effectives de l'effecteur terminal (105)
aux coordonnées absolues de l'effecteur terminal (105) stockées dans chacun des instants
d'échantillonnage ;
- si les coordonnées absolues effectives de l'effecteur terminal (105) sont les mêmes
que l'une des coordonnées absolues de l'effecteur terminal, stockées dans l'un des
instants d'échantillonnage, l'actionnement des actionneurs stockés pour effectuer
le déplacement de l'effecteur terminal vers la coordonnée absolue stockée à l'instant
d'échantillonnage suivant.
2. Système selon la revendication 1, dans lequel ladite étape de réexécution du déplacement
de l'effecteur terminal (105) comprend en outre :
- s'il est déterminé, sur la base de la configuration du bras articulé, que l'effecteur
terminal (105) n'est pas capable d'atteindre la coordonnée absolue stockée à l'instant
d'échantillonnage suivant, l'actionnement en outre d'un ou de plusieurs actionneurs
supplémentaires selon une logique opérationnelle prédéterminée.
3. Système selon la revendication 1 ou 2, dans lequel ladite étape de stockage dans le
module de mémoire des coordonnées absolues de l'effecteur terminal (105) est effectuée
sans stockage de la configuration du bras articulé susceptible d'être obtenue par
les signaux desdits capteurs.
4. Système selon l'une quelconque des revendications précédentes, dans lequel ladite
étape de stockage dans le module de mémoire des actionneurs utilisés pour déplacer
l'effecteur terminal (105) est réalisée sans stocker les sens de déplacement et l'étendue
des déplacements des actionneurs.
5. Système selon l'une quelconque des revendications précédentes, dans lequel ladite
étape de comparaison des coordonnées absolues effectives de l'effecteur terminal (105)
aux coordonnées absolues de l'effecteur terminal (105) stockées dans chacun des instants
d'échantillonnage est réalisée avec une tolérance prédéfinie.
6. Système selon l'une quelconque des revendications précédentes, dans lequel ladite
étape de réexécution du déplacement de l'effecteur terminal (105) comprend en outre,
si les coordonnées absolues effectives de l'effecteur terminal (105) ne sont pas les
mêmes que l'une des coordonnées absolues de l'effecteur terminal stockée dans l'un
des instants d'échantillonnage :
- la détermination de la trajectoire globale stockée de l'effecteur terminal (105)
;
- si la coordonnée absolue effective de l'effecteur terminal (105) se trouve dans
un segment de la trajectoire compris entre une première et une seconde coordonnées
absolues stockées entre deux instants d'échantillonnage suivants, l'actionnement des
actionneurs stockés pour effectuer le déplacement de l'effecteur terminal (105) entre
lesdites deux coordonnées absolues stockées entre deux instants d'échantillonnage
suivants ;
- s'il est déterminé, sur la base de la configuration du bras articulé, que l'effecteur
terminal (105) n'est pas capable d'atteindre la seconde coordonnée absolue stockée,
l'actionnement d'un ou de plusieurs autres actionneurs selon une logique opératoire
prédéterminée.
7. Système selon la revendication précédente, dans lequel ladite étape de réexécution
du déplacement de l'effecteur terminal (105) comprend en outre, si la coordonnée absolue
effective de l'effecteur terminal (105) se trouve en dehors de la trajectoire stockée
:
- le calcul du point de la trajectoire stockée, le plus proche de la coordonnée absolue
effective de l'effecteur terminal (105) ;
- l'actionnement des actionneurs selon une logique prédéterminée pour déplacer l'effecteur
terminal (105) vers ledit point.
8. Système selon l'une quelconque des revendications précédentes, dans lequel le temps
de réexécution partiel est égal au temps d'échantillonnage.
9. Système selon l'une quelconque des revendications précédentes, dans lequel l'unité
de commande est configurée pour recevoir, comme paramètre d'entrée, un temps de réexécution
global souhaité, dans lequel ladite étape de réexécution du déplacement de l'effecteur
terminal (105), si le temps de réexécution global souhaité est différent du temps
de déplacement global de l'effecteur terminal pendant l'étape de stockage, comprend
:
- la détermination de la trajectoire stockée de l'effecteur terminal (105) ;
- le calcul, sur la trajectoire stockée, des coordonnées absolues équivalentes de
l'effecteur terminal, correspondant aux coordonnées absolues de l'effecteur terminal
qui seraient détectées à l'étape de stockage du déplacement si l'effecteur terminal
avait effectué la trajectoire déterminée dans le temps de réexécution global souhaité
;
- la fixation des coordonnées absolues stockées de l'effecteur terminal égal auxdites
coordonnées absolues équivalentes.
10. Système selon la revendication précédente, dans lequel ladite étape de réexécution
du déplacement de l'effecteur terminal (105) comprend en outre :
- si le temps de réexécution global souhaité est supérieur au temps de déplacement
global de l'effecteur terminal pendant l'étape de stockage, le stockage, pour chaque
coordonnée absolue équivalente, des actionneurs stockés le long du segment de la trajectoire
sur lequel se trouve la coordonnée absolue équivalente ;
- si le temps d'exécution global souhaité est inférieur au temps de déplacement global
de l'effecteur terminal pendant l'étape de stockage, le stockage, pour chaque coordonnée
absolue équivalente, des actionneurs utilisés dans le segment de la trajectoire sur
lequel se trouve la coordonnée absolue équivalente et dans tous les segments précédents.
11. Système selon l'une quelconque des revendications précédentes, dans lequel ladite
unité de commande est configurée pour effectuer une commande en boucle fermée de la
trajectoire entre une première coordonnée absolue et une seconde coordonnée absolue
de l'effecteur terminal (105).
12. Système selon l'une quelconque des revendications précédentes, dans lequel lesdites
coordonnées absolues de l'effecteur terminal (105) sont des coordonnées cartésiennes
absolues dans un espace 3D.
13. Système selon l'une quelconque des revendications précédentes, dans lequel ledit bras
articulé (101) comprend une grue articulée.
14. Système selon la revendication précédente, dans lequel ladite grue articulée comprend
une colonne (102) rotative autour de son axe, un bras principal (103') rotatif autour
de la colonne (102), un bras secondaire (103") rotatif autour du bras principal (103')
et comprenant au moins une extension déployable en translation à partir du bras secondaire
lui-même, et ladite pluralité de capteurs comprennent un capteur angulaire permettant
de mesurer la rotation de la colonne (102) autour de son axe, un capteur angulaire
permettant de mesurer la rotation du bras principal (103'), un capteur angulaire permettant
de mesurer la rotation du bras secondaire (103"), un capteur linéaire permettant de
mesurer la translation de l'extension (104) à partir du bras secondaire (103").