Collaborative handling robot with mixed force control laws providing high effector sensitivity and allowing interaction with the robot's body - Patents.com

Abstract

A collaborative process robot is disclosed having a mixed force control law that provides high effector sensitivity and allows interaction with the robot's body. The invention essentially consists of carefully positioning a multi-axis force sensor between the end member (flange) of an industrial collaborative process robot and the implement supported thereby, and modifying the increased force control law implemented in the robot controller by introducing a saturation function.

Description

[Technical Field]

[0001] This invention relates to the field of robotics, and more particularly to physical human-robot interaction (pHRI) utilized by collaborative processing robots.

[0002] Generally speaking, pHRI is an action that allows a human operator to enter the robot's work area, enabling one to interact with the other directly and physically.

[0003] More specifically, this invention relates to a force-increasing control law for collaborative processing robots. [Background technology]

[0004] In the field of robotics, there are various systems that allow operators to be assisted during operations.

[0005] To process objects remotely and perform laborious tasks, there are systems called remotely operated systems. Such systems generally consist of a control arm and a controlled arm coupled to it.

[0006] However, these are complex systems in both their design and use. Therefore, they can be costly and difficult to master. Generally speaking, the manufacturability achieved by systems is inferior to that achieved by working directly on components, either by hand or through tools.

[0007] To assist operators in performing complex and / or laborious tasks while simultaneously maintaining simpler systems than remotely operated systems, systems called collaborative processing systems have been developed. These systems generally consist of collaborative processing robots or joint robots that perform tasks that would otherwise be accomplished using tools, and are equipped with guide members that allow a human operator to control the movement of the collaborative processing robot via the guide members.

[0008] Cooperative processing thus enables the robot and the operator to jointly manipulate the tool so as to assist the operator in performing the tasks to be achieved accordingly.

[0009] More generally, such a mode of interaction between humans and robots can provide several functions for assisting operations, such as compensating for the weight of the tool, applying programmable mechanical constraints, and increasing force.

[0010] Thus, through cooperative processing, various learning / programming functions are executed in situ by guiding the robot in terms of the points involved in the operation, movement and / or force, and then the operation will be automatically performed by the same robot.

[0011] The suitability of a robot for cooperative processing mainly depends on its sensitivity to the force applied by the operator and its environment with respect to its end element or member having the tool or gripper. The quality of cooperative processing as felt by the operator is highly related to the concept of mechanical transparency achieved by the robot system (robot mechanism, sensors, and actuators following control laws).

[0012] The transparency of a robot system describes its ability to move in an unconstrained direction while minimizing the force of interaction with the operator and / or its environment.

[0013] A system exhibiting complete transparency can follow the movement applied to the tool by the operator in the constrained space without offering any resistance to such movement, and the obstacles caused by the robot are not recognized by the operator.

[0014] Robot systems capable of enabling cooperative processing can be classified into three different categories.

[0015] The first relates to a mechanically transparent coupled system. The mechanical design of the actuator allows for excellent force transmission both from the motor to the segments and terminal members, and from the segments and terminal members to the motor. In addition to any constraints, which may be on displacement, the control laws need to compensate only for the weight of the robot and instrument, as experienced by the joints, in order to enable transparent cooperative processing, as disclosed in Publication [1] and Patent Document 1.

[0016] The second type is a system with insufficiently transparent joints. Mechanical friction within the joints, including reduction gears and motors, transmitted to the point of interaction with the operator during the process of movement, exceeds the difficulty threshold.

[0017] Finally, there are systems with irreversible joints. With zero motor force, no matter what force is applied to the robot by the operator, these joints will become immobile, and movement will not be possible. This is especially true for joints created with worm / wheel type mechanical systems with high reduction ratios.

[0018] This invention relates solely to the category of systems with insufficiently transparent and / or irreversible joints, which currently constitutes the majority of industrial robots on the market. In particular, industrial robots have been designed to optimize positioning accuracy / repeatability at the expense of their ability to interact with human operators.

[0019] The inventor therefore sought to improve the collaborative processing of existing industrial robots with joints that are insufficiently mechanically transparent or irreversible.

[0020] The inventor analyzed the various shortcomings and limitations of these existing robots and itemized all currently available solutions.

[0021] First, the collaborative processing of the apparatus needs to be performed with greater transparency than that inherent to the machine, especially with significantly reduced joint friction. To overcome the mechanical limitations to transparency in the system, which are insufficiently transparent, the first solution consists of modeling the joint frictional forces in order to add compensation for this to the actuator control laws.

[0022] This solution is largely unsatisfactory for current industrial robots because the friction model depends on parameters that vary greatly with joint lubrication, temperature, and wear. Furthermore, the variations in friction are abrupt and extremely nonlinear around zero velocity. Compensation for friction is therefore inoperable for precise or slow movements, as is evident from publications [2].

[0023] Furthermore, the robotic system being implemented will have less sensitivity than the equipment itself needs to possess, but it must remain sensitive throughout the entire robot body.

[0024] In systems with insufficiently transparent or irreversible joints, one solution is to install force sensors between the terminal segment or member and the instrument to measure six components of the loading pattern (three force components and three torques). The predicted weight of the instrument is subtracted in advance from the force measurement. A closed-loop feedback control law is then implemented in robot control to hold this force measurement at zero in the actuator. This allows the robot system to move in a continuous manner so as to cancel out the forces of the interaction between the robot and the operator in each case. The internal frictional forces of the joint are thus rejected, whatever their nature may be, without requiring any form of predictive calculation:[3].

[0025] This solution, therefore, allows for the complete rejection of frictional forces in accordance with the implementation of the control laws. In contrast, it is impossible to overcome the effects of the robot's mechanical inertia:[4].

[0026] In particular, the control laws associated with the gain adjustment are described as passive when the controlled robotic system is stable in any mechanically passive environment and in its interaction with a human operator (which may itself be considered passive[6][5]). Next, it has been theoretically shown that in simple correction devices, adjustments that overcompensate for the robot's inertia are no longer passive and are particularly unstable when in contact with highly rigid environments or instruments with high inertia.

[0027] Furthermore, a major limitation of this solution for measuring forces on terminal elements is that it excludes any inertia between the robot body and its environment. In particular, feedback control indiscriminately rejects friction and all interacting forces upstream of the force measuring sensor because they are not measured. This can lead to inattention to situations where the robot body exerts considerable and potentially destructive forces on elements in the workspace or other operators, especially when the operator is primarily focused on moving the tool.

[0028] Another limitation of this solution is that it is difficult to master robot reconfiguration movement in the immediate vicinity of the robot's sole configuration, because the force projection measured at a particular joint is zero or extremely low. For the same reason, in the case of a robot with redundant kinematics, internal robot movement that does not result in any displacement of the terminal members (terminal segments) cannot be controlled by collaborative processing of the instrument alone. In an anthropomorphic arm with seven degrees of freedom, it is impossible for the operator to control the position of the elbow during collaborative processing without interacting with the robot body.

[0029] Furthermore, robotic systems with mechanically insufficiently transparent or irreversible joints need to remain sensitive throughout the entire body of the robot, even if this means lower sensitivity in the instrument.

[0030] To achieve this, one solution is to cover the surface of the robot body segments with a pressure-sensitive layer.

[0031] Patent document 2 proposes a solution in which the robot body is covered with skin, thereby transmitting a signal to the robot if it comes into contact with an element in the workspace beyond the detection threshold of the skin, and stopping its movement until the contact is removed. This generally requires engaging and disengaging the robot using some other means, such as a pendant.

[0032] Particularly highly evolved skins, such as those described in Patent Document 3, enable the determination of the location and intensity of contact, thereby stopping only those components of movement in the direction of contact, while leaving others free. This allows for better continuity of collaborative processing.

[0033] A drawback of using skin is that, by definition, the skin needs to be adapted to the specific geometric shape of each robot. Another drawback is that it is not possible for the operator to collaboratively manipulate the robot body with their second hand, for example, even though it would be practical to control the robot's configuration in the vicinity of the robot or during collaborative processing through the robot's kinematic unity.

[0034] An alternative solution for good sensitivity across the entire robot body is to adapt a force sensor that measures six components (three force components and three torques) of the loading pattern between the robot base and its pliers. Thus, the forces applied to the robot body and instrument are actually measured by the sensor within the base. Since a full gravity model may be sufficient for slow movements, as described in publication [7] or patent document 4, it is sufficient to reuse the same law for a force sensor positioned on the terminal member, by subtracting from the measured value the predicted dynamic loading pattern of the robot which is reduced to the sensor within the base.

[0035] The drawback of this solution is that the weight of the robot is actually much greater than the force applied by the operator, and therefore requires load sensors with a much higher bore diameter that have much stricter requirements regarding the accuracy of measurements (noise, linearity, and drift) required for the force sensors on the robot's terminal members.

[0036] Another drawback of positioning force sensors between the robot's base and its principles is that the robot's seating needs to be particularly well controlled when the robot is being installed, as errors would otherwise be introduced into the prediction of the gravity loading pattern, and these would lead to considerable forces that disrupt collaborative processing.

[0037] The final drawback is that it affects collaborative processing of two hands on separate segments of the robot, and the internal force components against the robot's motion chain do not have the overall resultant force that can be measured by the force sensor at the base. Such a situation may occur, in particular, when the operator wants to flex the robot elbow by having the arm and forearm work together. This leads to obstacles in certain collaborative processing configurations.

[0038] Another alternative solution is to place joint torque sensors at the output of each robot joint, with one component per joint. This solution makes it possible to make the system fully sensitive to the forces that can be applied to all segments of the robot, even in the case of two-handed collaborative processing:[8], [9].

[0039] The drawback of this solution is that it requires a new design for the robot joints, something that cannot be added to existing industrial robots.

[0040] Finally, another alternative solution is to implement a force-increasing control law within the robot controller. Such a control law uses measurements (indirect measurements) of the motor force of a setpoint or actuator on the robot from sensors positioned to measure the force of a cooperative mechanical interface element on a device such as a handle, and from sensors positioned to measure the force of a cooperative mechanical interface element on a device such as a handle. m, for example, combine the measurement of motor current or actuator pressure.

[0041] Such control is described in particular in Patent Document 5.

[0042] As explained in publication

[10] , the principle of force increase control is as follows. The loading pattern of the measurement from a sensor positioned to measure the force of a cooperative processing mechanical interface element (e.g., a handle) on the instrument is F h shown, and its projection in the motor space is τ h shown. The vector of the setpoint or the measured value (indirect measurement value) of the motor force of each actuator on the robot is τ m shown. Then, the component of gravity known from the two measured / controlled parameters F h and τ m is considered to have already been compensated. The force in the work space on the instrument and the robot body (excluding the operator force F h ) is set as F t , and its projection on the same motor space is set as τ t , and the torque of the mechanical friction of the joint is set as τ f .

[0043] In equilibrium, the following mechanical relationship can be written. τ m +τ t +τ h +τ f =0 (1)

[0044] The force increase gain is then set as g f >1. τ ∈ is then defined as the error torque in the motor space and satisfies the following relationship: τ ∈ =-(τ m +τ h ) / g f +τ h .

[0045] In the same manner as the force control described earlier, closed-loop feedback control is then performed at the robot actuator setpoint to maintain the error torque at zero. At equilibrium, the following is observed: 0 = -(τ m +τ h ) / g f +τ h (2)

[0046] Substituting (1) into (2), we obtain the following:

[0047]

number

[0048] This equation shows the following: - On the one hand, the objective of increasing force is actually fulfilled. Aside from joint friction, the force that the instrument exerts on the workspace does not actually correspond to the force that the operator exerts on the collaborative processing interface multiplied by the force-increasing gain. - On the other hand, the device is not in contact (τ t If = 0, the robot joint friction experienced by the operator is divided by this same gain.

[0049] Since there is no difference between the force on the device and the robot body, such control thus offers the advantage of giving the robot body a specific sensitivity and increasing transparency in the collaborative processing interface.

[0050] A drawback of this solution is that there is a compromise reached regarding the force increase gain. This needs to be high enough to reduce the amount of friction experienced, but if it is too high, the sensitivity on the robot body becomes too low.

[0051] Another drawback is that the operator may interact with the robot body or the collaborative processing interface, but not both simultaneously. The robot's displacement does not correspond to the resultant force of the two interacting forces, which is then something that is not intuitive and difficult for the operator to control.

[0052] Therefore, there is a need to improve the collaborative processing of existing industrial robots with mechanically insufficiently transparent or irreversible joints, particularly to mitigate the aforementioned shortcomings, and more specifically, those of the force-increasing control law. [Prior art documents] [Patent Documents]

[0053] [Patent Document 1] International Publication No. 2014 / 161796 brochure [Patent Document 2] International Publication No. 2016 / 000005 Brochure [Patent Document 3] International Publication No. 2010 / 097459 Pamphlet [Patent Document 4] U.S. Patent Application Publication No. US2015 / 0290809A1 [Patent Document 5] International Publication No. 2015 / 197333 Pamphlet [Overview of the Initiative] [Problems that the invention aims to solve]

[0054] The objective of this invention is to satisfy this need at least partially. [Means for solving the problem]

[0055] To do this, one aspect of the present invention is: - A motion chain of mechanical elements comprising a near-end element and a distal-end element forming the base of a robot, wherein the various elements are mounted such that they have the ability to move relative to one another, such that the distal-end element can move relative to the near-end element. - An instrument and / or gripper intended to be operated by a human operator, the instrument and / or gripper being connected to a distal end element such that it has the same degrees of freedom as the distal end element, - Means for controlling at least a portion of the first chain of elements, Actuators positioned on the chain to perform all the movement of various elements of the chain relative to each other and / or to apply force in between, A means for measuring the displacement of elements relative to each other, In appropriate cases, means for measuring the force applied by the actuator, A single multi-axis force sensor is positioned between the distal end element and the instrument and / or gripper to measure the force applied to these, A control means comprising: a controller for controlling an actuator based on measurements obtained by means for measuring displacement and, where appropriate, means for measuring force applied by an actuator, and measurements from a multi-axis force sensor, according to control laws implemented within the controller; Regarding a collaborative processing robot equipped with the above, the control law is: - A force amplification loop configured to amplify a force applied to an instrument by an operator and measured by a multi-axis force sensor at a robot joint, wherein the measurement is with respect to at least some of the degrees of freedom at the distal end, and the force amplification loop comprises a comparator for subtracting the product of anti-wind-up gains Kaw from the product of integral gains Ki of the loop, and an integrator that receives the result from the comparator to supply setpoint velocities to various elements of the chain, - An internal velocity loop with a proportional gain Kv that receives the velocity setpoint from the force increasing loop in order to supply a non-saturating reference torque to various actuators, - saturation period τ sat The vector τ of the actuator's dry friction coefficient f0 An internal velocity loop saturation function is selected to be greater than or equal to this, - Includes an anti-windup component obtained as the product of saturation and a force correction added by gain Kaw, which is again supplied to the input of the force amplification loop's integrator, and as soon as saturation is achieved, the force amplification loop's integrator blocks its integral.

[0056] Relationship Kaw = Kv -1 It is preferable that this is set.

[0057] More preferably, saturation period τ sat is vector τ f0 It is equal to the sum of the above uncertainty values ​​plus twice each.

[0058] In the context of this specification and the present invention, the term "controller" is used in a broad sense, meaning a combination of hardware and software for programming and controlling a robot.

[0059] According to the first configuration, if the actuator can be directly controlled by force via a controller, the saturation function is directly applied at the output of the internal velocity loop.

[0060] According to the second configuration, the actuator cannot be directly controlled by force, but if it is controlled, for example, by a closed position or speed controller, the force τ applied by the actuator m This is then measured and examined in saturation calculations.

[0061] Preferably, the means for measuring the displacement of the elements relative to each other includes an absolute position sensor, or even an absolute multi-swivel sensor, if it is placed directly on the motor output before the deceleration phase.

[0062] The controller may be configured to implement additional control laws selected from, for example, control with programmable virtual mechanical constraints, control with Cartesian or joint velocity limits, control with workspace constraints, and remote control with or without force feedback. For control with programmable virtual mechanical constraints, Cartesian or joint velocity limits, or workspace constraints, refer to the teachings in Patent Document 5.

[0063] Remote control with or without force feedback may implement the laws described in

[11] or

[12] .

[0064] Therefore, the present invention basically consists of intelligent positioning of a multi-axis force sensor between the terminal member (flange) of a collaborative processing industrial robot and the equipment it has, and modification of the force increase control law implemented within the robot's controller by adding a saturation function.

[0065] The present invention therefore makes it possible to mitigate the drawbacks of the force increase law of the prior art, thereby enabling increased sensitivity on the robot body and allowing a human operator to interact with the robot body and collaborative processing interfaces such as devices supported by the robot's terminal members.

[0066] In other words, the control according to the present invention combines highly sensitive force measurements of multi-axis sensors with force measurements or setpoints on the actuators, which on the other hand ensure an improvement in sensitivity to physical interaction with the entire robot body, albeit with a significantly reduced force (a high level of transparency such as hiding the mechanical friction of the robot joints) to displace the robot by directly manipulating the instrument.

[0067] Therefore, in the event of an accidental collision with an obstacle in the environment, the operator can easily operate the equipment supported by the robot without worrying about the robot itself applying excessive force.

[0068] When this happens, the control system respects the "natural" equilibrium of forces, so that opposing forces cancel each other out, and the robot stops without applying a greater force to the obstacle than the operator is applying to the device.

[0069] In addition to collaborative processing capabilities on industrial robots, this invention offers numerous advantages. - A significant reduction in joint mechanical friction experienced by human operators when directly handling instruments in a collaborative manner. - Sensitivity of the robot body to forces of interaction with the operator and / or workspace, - The “natural” balance of forces that is respected in the case of numerous joint interactions between the operator, workspace, robot body and equipment, even when internal force components are present. - Passivity of the interaction between the robot and its working environment as a result of the stability obtained when in contact with any passive environment, - It does not require any modification of the mechanical architecture of the robot or its actuators. - There is no need to cover the robot body with elements that are sensitive to contact. - There are no restrictions on use when approaching or passing through the mechanical unity of a robot. - The possibility of combining control laws with other additional control laws useful for collaborative processing (such as virtual constraints, speed limits and workspace limits, remote control, etc.) These are some examples.

[0070] None of the conventional solutions proposed for controlling industrial collaborative processing robots can simultaneously provide all of these advantages.

[0071] Another subject of the present invention is the use of industrial collaborative processing robots, as described above, as robots to assist in surgical interventions, or as robots to assemble or process heavy loads, or as read-through programming robots.

[0072] Further advantages and characteristics of the present invention will become more apparent from reading the detailed description of the exemplary embodiments of the invention given as non-limiting examples and referring to the following drawings. [Brief explanation of the drawing]

[0073] [Figure 1] This is a schematic diagram of an example of an industrial collaborative processing robot equipped with a controller, which is used as a system to increase the force applied by a human operator to equipment being handled by the robot. [Figure 2] This diagram summarizes all the forces applied to the system in Figure 1. [Figure 3] This figure shows the control law according to the present invention, as executed by the robot controller shown in Figure 1. [Figure 4] This figure shows a modified form of the control law according to the present invention. [Modes for carrying out the invention]

[0074] Figure 1 shows an industrial collaborative processing robot 1 according to the present invention, which is used as a system to assist in the operation of equipment.

[0075] In the illustrated example, the instrument is a needle used by a surgeon for surgical intervention in an operating room, which constitutes the working environment of robot 1. In this illustrated example, collaborative robot 1 is controlled by a mixed force control law, described in detail below, which allows a human operator (surgeon) to manipulate the instrument together with the robot, while simultaneously remaining sensitive to interaction with the robot body and compensating for the weight and friction of the instrument within the robot joints.

[0076] This law can be combined with additional control laws that impose virtual guidance constraints on the device (which are not described in detail here in the context of this invention).

[0077] Collaborative processing robot 1 is a robot having a manipulator arm with six degrees of freedom.

[0078] Therefore, the robot 1 comprises a motion chain of interconnected elements, a nearby end element 2 forming the base of the robot, and a distal end element 3 forming the flange. In addition, it comprises two elements 4, 5 or segments interconnected between the base 2 and the distal end element 3.

[0079] Robot 1 also includes a device, which is a needle 6, fixed to a handle 7 operated by a human operator in the illustrated example. The needle 6 and handle 7 are connected to the distal end element 3 (flange) such that they have the same degrees of freedom as their respective elements, i.e., six degrees of freedom relative to the base 2.

[0080] Therefore, the needle 6 can be moved in all directions in space when it is translated and rotated relative to the base 2.

[0081] The operator may interact with the instruments 6, 7 and / or the body of the robot, in particular its element 5, within the interaction area IZ.

[0082] The workspace may also interact with the instrument 6 and / or the body of the robot, and in particular its element 4, in the event of intentional or unintentional (unwanted) contact with the operator.

[0083] In other words, there are two interaction ports directly installed on the robot: one via the robot body, particularly its elements 4 and 5, and the other via devices 6 and 7.

[0084] The robot further includes means for controlling the chain of elements, and thus devices 6 and 7 connected to the distal end element 3.

[0085] The control system first includes a controller 10 that executes a program to control the main chain of robot elements in order to maintain coordination between the robot body and the devices 6 and 7.

[0086] The control means also includes actuators, not shown, positioned at each joint in the chain of elements, to enable the movement of one element relative to an adjacent element of the corresponding joint, or to apply force between these elements. The controller 10 controls the various actuators, as schematically shown by the arrows 11 in Figure 1, so that the devices 6, 7 can be moved in a coordinated manner relative to the base 2.

[0087] Furthermore, a multi-axis force sensor 8, preferably a 6-axis sensor, is positioned between the distal end element 3 and the instruments 6, 7, as indicated by arrow 12 in Figure 1, to enable the controller 10 to generate signals indicating the force applied to the distal end element 3 by the instruments 6, 7. The instruments 6, 7 are therefore connected to the distal end element 3 via the multi-axis force sensor 8.

[0088] The control means further includes means for measuring the displacement of various elements, and here, as indicated by arrow 13 in Figure 1, it includes multiple position sensors (not shown) positioned at each of the joints of the main chain of elements, so that the controller 10 can generate a signal indicating the relative position of the two elements forming the joint. The position sensors are absolute position sensors.

[0089] The absolute position sensor and multi-axis force sensor 8 thus enable the controller 10 to measure the movement of the instruments 6, 7 and the robot body relative to the base 2 at any moment, and the force applied to the instruments 6, 7 at any moment.

[0090] According to the present invention, the controller 10 executes a program according to control laws described in detail below, which enable increased sensitivity to the force applied to the devices 6, 7 by the operator or their environment.

[0091] This control law may be combined with other additional control laws, not described in detail herein, which, as shown in Figure 1, allow for the addition of a virtual constraint 14 to the displacement of the instrument in order to guide the insertion of the needle 6 into the patient B's body toward the area of ​​interest.

[0092] Subtracting the known weights of the devices 6 and 7 and reducing the load pattern for the force applied to the distal end element 3 of the robot, as measured by the force sensor 8, is shown as in [Equation 2], where this component is shown at the base of the sensor frame of reference S.

[0093]

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[0094]

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[0095] In equation [Equation 3], [Equation 4] is the resultant force, and [Equation 5] is the torque at point S of the measured force, which are shown in the frame of reference S.

[0096]

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[0097]

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[0098] The Cartesian position of the frame of reference S, indicated by the frame of reference E associated with the robot's terminal member, is X S,E This is denoted by ∈SE(3). Since the force sensor 8 is rigidly connected to the distal end element 3, X S,E is a constant and can be decomposed into [Equation 6], i.e., the rotation matrix of the frame of reference S within the frame of reference E, and [Equation 7], i.e., the original position of the frame of reference S as shown in the frame of reference E.

[0099]

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[0100]

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[0101] This results in the following equation.

[0102]

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[0103] Reduced to the center of the frame of reference E, and shown therein is the loading pattern in response to the force applied by sensor 8 to the distal end element 3 of the robot.

[0104] The vector of the measured position of the robot joints is shown as in [Equation 9], where N is the number of joints.

[0105]

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[0106] The vector of the measured position of the robot actuator is shown as in [Equation 10], where P ≤ N is the number of robot joints.

[0107]

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[0108] At a given joint position q, the Cartesian position of the frame of reference E associated with the robot's terminal member, as shown on the frame of reference B at the base of the robot, is X = X E,B (q) ∈ SE(3). This position can be decomposed into [Equation 11], which is the rotation matrix for the rotation of the frame of reference E in the frame of reference B, and [Equation 12], which is the original position of the frame of reference E shown in the frame of reference B.

[0109]

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[0110]

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[0111] This results in the following equation.

[0112]

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[0113] This is the load pattern applied to the robot's terminal member by a sensor that is reduced to the center of the frame of reference E, as shown in the frame of reference B.

[0114] Jacob Matrix X as an application example E,B (q) is shown as [Equation 14] and is [Equation 15], where [Equation 16] is the kinematic load pattern on the robot effector that decreases to the center of the frame of reference E, shown in the frame of reference B, and can be decomposed into [Equation 17], i.e., the velocity at the origin of the frame of reference E shown in the frame of reference B, and [Equation 18], i.e., the rotational velocity vector relative to the frame of reference E shown in the frame of reference B.

[0115]

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[0116]

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[0117]

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[0118]

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[0119]

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[0120] The matrix for the deceleration ratio from actuator space to joint space is shown below.

[0121]

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[0122] This then becomes the load pattern W for the force applied to the terminal member by the sensor, [Number 20]. S Projection of into actuator space, τ S =G T .J T .W S This makes it possible to obtain.

[0123]

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[0124] All forces applied to the system are then considered within the actuator space, and these are summarized in Figure 2.

[0125] The force vectors applied to the robot body projected into actuator space by the operator and the workspace are shown below.

[0126]

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[0127] The vector of the force generated by the actuator (measured or setpoint force) is shown as follows:

[0128]

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[0129] The vector of the joint friction force projected into the actuator space is shown as follows:

[0130]

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[0131] The gravitational force vector projected into the actuator space of a robotic device system is shown as follows:

[0132]

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[0133] The centrifugal and Coriolis force vectors projected into the actuator space of the robotic device system are shown below.

[0134]

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[0135] The inertia matrix of the robotic device system projected into actuator space is shown below.

[0136]

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[0137] At equilibrium and low speed [Equation 27], the following relationship applies: タウs +τ b +τ g +τ f +τ m =0 (3)

[0138]

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[0139] The mixed force control law according to the present invention is shown in Figure 3.

[0140] The following loop is performed within controller 10: - Strength increase loop 100, - An internal velocity loop 101 receives the velocity setpoint from a force increasing loop in order to supply setpoint torque to various actuators. - Internal velocity loop saturation function 102, - Prediction for compensation of Model 103.

[0141] The various interactions between the loops are described in detail below, with reference to the robot actuator space.

[0142] The vector of the gravitational force model of the robotic device system, projected into actuator space, is shown below.

[0143]

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[0144] The vectors of the joint friction force model projected into the actuator space are shown below.

[0145]

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[0146] An example of a friction model confined to the actuator space may be [Equation 30], where [Equation 31] represents the vector of the dry friction coefficient of the actuator, [Equation 32] represents the nominal speed of an application example of the model, and [Equation 33] represents the damping within the actuator.

[0147]

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[0148]

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[0149]

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[0150]

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[0151] The following notation is introduced to simplify the relationship with force amplification control, as described in

[10] .

[0152] τ h =τ s [Equation 34] shows the force projected into the actuator space of an interaction port whose sensitivity increases, in the inventor's example, an instrument attached to a force sensor. [Equation 34] shows the force projected into the actuator space of other interaction ports whose sensitivity does not increase, in this example, all predictions of external forces applied to the robot body.

[0153]

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[0154] Therefore, the following equation is obtained. Here, g f >1 indicates the amplification factor of the force increasing loop.

[0155]

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[0156] [Equation 36] is the integral gain of the force amplification loop. K iThis gain is inversely proportional to the apparent inertia of the controlled system. The theoretical constraint for setting this gain, and therefore to the achievable apparent inertia of a robot controlled according to a passive criterion, namely the unconditional stability of a robot interacting with any passive environment, is approximately the mechanical inertia inherent to the robot:[4].

[0157]

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[0158] The setpoint force vectors derived from any additional control laws not described in detail here are shown as in [Equation 37], where the law may be a virtual constraint law, a velocity limiting law, a working space limiting law, or a remote control law.

[0159]

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[0160] At equilibrium and outside the saturation range, the integrator input is zero, and the properties of the force amplification loop are therefore actually faced [Equation 38].

[0161]

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[0162] By substituting (3) and (4) into (5), we obtain the following:

[0163]

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[0164]

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[0165] Therefore, the friction not compensated by model [equation 41] is actually τb =0, τ ref It can be seen that the force amplification factor is reduced when the operator is simply using the equipment, corresponding to =0 and [Equation 42].

[0166]

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[0167]

number

[0168] [Equation 43] shows the proportional gain of the internal velocity loop 101. The purpose of the internal velocity loop is to linearize the system, particularly with respect to dry friction, thereby reducing the accumulation required in the integrator of the force amplification loop and improving friction rejection, especially at the point of change as a marker of joint velocity.

[0169]

number

[0170] [Equation 44] is the saturation period for the velocity loop 101. The saturation function makes it possible to limit the contribution of force amplification to just match the decrease in dry friction, allowing for a "natural" equilibrium of forces when there are joint interactions on the instrument and on the body of the robot.

[0171]

number

[0172] To do this, according to the present invention, τ sat is the degree τ f0 Selected to be so, and therefore, |τ h |>>|τ f0 Therefore, control is always saturated at equilibrium.

[0173] Equation (3) then becomes [number 45], and within the equation, [number 46].

[0174]

number

[0175]

number

[0176] The "natural" balance of forces is therefore actually restored, τ h ≒-τ b This is the result.

[0177] [Equation 47] shows the anti-wind-up gain of the integrator in a force-increasing loop of 100, which is necessary for the integrator to stop integrating as soon as saturation is achieved. It is favorably chosen to be as shown in [Equation 48].

[0178]

number

[0179]

number

[0180] Finally, [Equations 49] and [Equations 50] are the proportional gains of the force amplification loop corresponding to the two interaction ports described above. By adjusting these, it is possible to optimize the stability and passband of the force amplification loop, as specified in publication

[10] .

[0181]

number

[0182]

number

[0183] Force setpoint τ m is the prediction period τ of any additional control laws, namely modeling friction and gravity, [Equation 51] and [Equation 52]. ref is obtained by adding.

[0184]

Equation

[0185]

Equation

[0186] The inventors implemented the force control law with the saturation function described so far in the controllers for industrial robots from the Staubli ranges TX2_90 and TX2_60L. The collaborative processing performance was proven. The functionality that requires virtual constraints, speed limits, and a limited working space was well combined without loss of performance.

[0187] Changes to the control law according to the present invention are shown in the figure of FIG. 4. Such changes are applied to actuators that cannot be directly controlled by force. These may be, for example, hydraulic or pneumatic actuators fitted to servo valves.

[0188] Here, the speed setpoint [Equation 53] at the output of the force amplification loop 100 then directly controls an actuator that needs to have the ability to measure the force τ m

[0189]

Equation

[0190] In the case of a hydraulic actuator, the setpoint may be that of the servo-controlled hydraulic flow rate at the measured actuator pressure.

[0191] As schematically shown in Figure 4, the force τ m The measurements are therefore taken on the robot body on one hand, and on the other hand, saturation and anti-windup τ aw In calculations, it is used to calculate the force estimate [Equation 54].

[0192]

number

[0193] The present invention is not limited to the examples described herein, and the characteristics from the illustrated examples may be combined with each other in modified forms not shown.

[0194] Other modifications and improvements may be conceived in any way without departing from the scope of the present invention.

[0195] The actuator may advantageously include a servo motor. Generally, the actuator may include an ironless DC motor, a brushless motor, a conventional DC motor, a shape memory alloy, a piezoelectric actuator, an active polymer, a pneumatic or hydraulic actuator. The actuator may have brakes on one or more elements of the robot body. These brakes may therefore be disc brakes, powder brakes, or magnetic fluid or electrofluid brakes. The actuator may also include a hydraulic actuator with both a motor and a brake or reverse-acting device and / or a variable stiffness device. If the actuator includes, for example, a reduction gear associated with the motor, the reduction gear may be of any type, for example, a simple gearing or planetary gearing reduction motor, a “Harmonic Drive” type reduction gear or a ball screw reduction gear or a cable winch reduction gear in one or more stages. Instead of a reversible reduction gear, it is possible to have an irreversible reduction gear such as a worm and wheel reduction gear.

[0196] (References) [1] B. Rooks, “The harmonious robot”, Industrial Robot: An International Journal, vol. 33, n° %12, pp. 125-130, 2006. [2] P. Hamon, M. Gautier and P. Garrec, “New dry friction model with load- and velocity-dependence and dynamic identification of multi-DOF robots”, IEEE International Conference on Robotics and Automation, pp. 1077-1084, 2011. [3] W. S. Newman and Y. Zhang, “Stable interaction control and coulomb friction compensation using natural admittance control”, Journal of Robotic Systems, vol. 11, n° %11, pp. 3-11, 1994. [4] W. S. Newman, “Stability and performance limits of interaction controllers”, Journal of Dynamic Systems, Measurement, and Control, vol. 114, n° %14, pp. 563-570, 1992. [5] J. E. Colgate, “The Control of Dynamically interacting Systems”, PhD Thesis, Massachusetts Institute of Technology, 1988. [6] N. Hogan, “Controlling impedance at the man / machine interface”, IEEE International Conference on Robotics and Automation, Proceedings, vol. 3, pp. 1626-1631, 1989. [7] F. Geffard et al., “On the use of a base force / torque sensor in teleoperation”, Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings, vol. 3, pp. 2677-2683, 2000. [8] A. Albu-Schaeffer and C. Ott, “A Unified Passivity Based Control Framework for Position, Torque and Impedance Control of Flexible Joint Robots”, The International Journal of Robotics Research, vol. 26, 2007. [9] R. B. et al., “The KUKA-DLR Lightweight Robot arm - a new reference platform for robotics research and manufacturing”, ISR 2010 (41st International Symposium on Robotics) and ROBOTIK 2010 (6th German Conference on Robotics), pp. 1-8, 2010.

[10] X. Lamy et al., “Human force amplification with industrial robot: study of dynamic limitations”, IEEE / RSJ International Conference on Intelligent Robots and Systems (IROS)., 2010.

[11] K. Hashtrudi-Zaad and SE Salcudean, “Analysis of Control Architectures for Teleoperation Systems with Impedance / Admittance Master and Slave Manipulators”, The International Journal of Robotic Research, vol. 20, n° %16, pp. 419-445, 2001.

[12] A. Micaelli, “Teleoperation et telerobotique, chapitre 6, asservissement et lois de couplage en teleoperation [Remote operation and remote robotics, chapter 6, feedback control and coupling laws for remote operation]”, Hermes science, 2002. [Explanation of Symbols]

[0197] 1. Industrial collaborative processing robot 2 nearest end elements 3. Distal end element 4 elements 5 elements 6 needles 7 Handle 8. Multi-axis force sensor 10 Controllers 11 Arrows 12 Arrows 13 Arrows 100 Power Increase Loop 101 Internal velocity loop 102 Internal velocity loop saturation function 103 Model

Claims

1. A kinematic chain of mechanical elements (2 to 5) comprising a proximal element and a distal element (3) forming the base (2) of a robot, the mechanical elements of the kinematic chain being attached with the ability to move relative to each other such that the distal element is movable relative to the proximal element, An instrument (6, 7) and / or a gripper intended to be operated by a human operator, the instrument (6, 7) and / or the gripper being connected to the distal element so as to have the same degrees of freedom as the distal element, Means for controlling at least a part of the kinematic chain of the mechanical elements, An actuator arranged on the kinematic chain of the mechanical elements to effect all of the movements of the mechanical elements of the kinematic chain relative to each other and / or to apply a force therebetween, Means for measuring the displacements of the mechanical elements relative to each other, Means for measuring, where appropriate, the force applied by the actuator, A single multi-axis force sensor (8) arranged between the distal element and the instrument and / or the gripper so as to measure the force applied to the distal element and / or to the instrument and / or to the gripper, A controller (10) for controlling the actuator based on measurement values obtained by the means for measuring displacements and, where appropriate, the means for measuring the force applied by the actuator, and measurement values from the multi-axis force sensor, in accordance with a control law implemented in the controller (10), A collaborative robot (1) comprising, The control law being, A force-increasing loop (100) configured to amplify, at a robot joint, a force applied to the instrument or the gripper and measured by the multi-axis force sensor, the measurement being related to at least some of the degrees of freedom of the distal end element, and an anti-windup gain K ａｗ A force-increasing loop (100) comprising a comparator for subtracting the product of the anti-windup gain K from the product of the integral gain Ki of the force-increasing loop, and an integrator receiving the result from the comparator for supplying a setpoint velocity to the mechanical element of the motion chain An internal velocity loop (101) with a proportional gain Kv receiving the velocity setpoint from the force increase loop to supply an unsaturated reference torque to the actuator arranged on the kinematic chain of the mechanical elements, Saturation term τ ｓａｔ is the vector τ of the dry friction coefficient of the actuator ｆ０ and an internal velocity loop saturation function (102) selected to be greater than or equal to this is again supplied to the input of the integrator of the force increase loop, and as soon as saturation occurs, the internal speed loop saturation function and the anti-windup gain K cause the integrator of the force increase loop to block its integration, as the anti-windup component obtained as the product of the force correction applied by ａｗ and, Including, a collaborative robot (1).

2. The anti-windup gain K ａｗ whose product is Kv －１ equal to, the collaborative processing robot according to claim 1.

3. the saturation term τ ｓａｔ is the vector τ ｆ０ plus twice the sum of the values of the uncertainties thereon, the collaborative processing robot according to claim 1.

4. The collaborative robot according to claim 1, wherein the actuator can be directly controlled by the controller by force and the internal velocity loop saturation function is directly added at the output of the internal velocity loop.

5. The actuator cannot be directly controlled by force, and the force τ applied by the actuator ｍ is then measured and considered to select the saturation term of the internal speed loop saturation function, the collaborative processing robot according to claim 1.

6. The collaborative robot according to claim 1, wherein the actuator comprises a servo motor.

7. The collaborative processing robot according to claim 1, wherein the means for measuring the displacement of the mechanical elements relative to each other comprises an absolute position sensor.

8. The controller is configured to implement at least one additional control law selected from control with programmable virtual machine constraints, control with Cartesian and / or joint speed limits, control with workspace constraints, and teleoperation control with or without force feedback. The collaborative processing robot according to claim 1.

9. The multi-axis force sensor (8) is arranged between the handle (7) of the instrument and the instrument (6) so as to measure only the force applied to the handle. The collaborative processing robot according to claim 1.

10. Use of the industrial collaborative processing robot according to claim 1 as a robot for assisting a surgical intervention, or as a robot for assembling or handling heavy loads, or as a lead-through programming robot.

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