received by the International Bureau on 25 September 2017 (25.09.2017)

CLAIMS

1. A method for controlling a mechanical system having a plurality of components interlinked by a plurality of driven joints, the method comprising:

measuring the torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces;

receiving a motion demand signal representing a desired state of the system; implementing an impedance control algorithm, comprising solving an ordinary differential equation from inputs of the motion demand signal and the load signal, to form a target signal indicating a target configuration for each of the driven joints; measuring the configuration of each of the driven joints and forming a state signal representing the measured configurations; and

forming a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.

2. A method as claimed in claim 1 , comprising driving each of the driven joints in dependence on the respective drive signal.

3. A method as clamed in claim 2, wherein each of the driven joints is provided with a respective electric motor for driving motion at the joint and each drive signal is applied to the respective electric motor.

4. A method as claimed in claim 2 or 3, comprising repeatedly performing the second measuring step, the forming step and the driving step.

5. A method as claimed in claim 4, wherein the step of forming the set of drive signals is performed at higher frequency than the step of forming the target signal.

6. A method as claimed in any preceding claim, wherein implementing the impedance control algorithm comprises solving the ordinary differential equation from inputs of, for each driven joint, a respective mass, damper and spring term.

7. A method as claimed in any preceding claim, wherein the motion demand signal represents a desired configuration for each of the driven joints.

8. A method as claimed in claim 7, comprising:

receiving a primary motion demand signal representing a desired physical position of a part of the mechanical system;

performing an inverse kinematic computation to determine a configuration for each of the driven joints that would position the part of the mechanical system at the desired physical position; and

providing those configurations as the motion demand signal.

9. A method as claimed in claim 6, or claim 7 or 8 as dependent on claim 6, comprising:

receiving data representing desired impedance characteristics for the physical system in a first coordinate space; and

converting that data to, for each driven joint, a respective mass, damper and spring term.

10. A method as claimed in claim 9, wherein the first coordinate space is a non- Cartesian coordinate space.

11. A method as claimed in claim 9, wherein the first coordinate space is a topological space.

12. A method as claimed in claim 9, wherein the first coordinate space is a vector space.

13. A method as claimed in any preceding claim, wherein the impedance control algorithm is implemented in joint space.

14. A method as claimed in any of claims 1 to 6, wherein the motion demand signal represents a desired physical position of a part of the mechanical system.

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15. A method as claimed in claim 14, wherein the said step of implementing the impedance control algorithm comprises:

solving the ordinary differential equation to determine a target physical position of the part of the mechanical system;

performing an inverse kinematic computation to determine a configuration for each of the driven joints that is suitable for positioning the part of the mechanical system at the target physical position; and

forming the target signal as indicating those configurations as the target configurations for the driven joints.

16. A method as claimed in claim 15, comprising:

specifying additional information indicating a desired configuration of the mechanical system; and

the step of performing an inverse kinematic computation is performed so as to determine a configuration for each of the driven joints that is suitable for positioning the part of the mechanical system at the target physical position and satisfying the desired configuration specified by the additional information.

17. A method as claimed in any preceding claim, comprising converting the measured torques or forces about or at the driven joints to a first coordinate space different from the space in which they were measured so as to form the load signal.

18. A method as claimed in claim 17, wherein the first coordinate space is a non- Cartesian space.

19. A method as claimed in claim 17, wherein the first coordinate space is a topological space.

20. A method as claimed in claim 17, wherein the first coordinate space is a vector space.

21. A method as claimed in any preceding claim, wherein the mechanical system is a robot manipulator.

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22. A method as claimed in any preceding claim, wherein the mechanical system is a surgical robot.

23. A method as claimed in any preceding claim wherein the mechanical system is a master-slave manipulator and the motion demand signal is formed by a master controller.

24. A controller for a mechanical system, the controller being configured to perform a method as set out in any preceding claim.

25. A robot manipulator having a plurality of components interlinked by a plurality of driven joints and a controller configured for controlling the manipulator by the method of any of claims 1 to 23.

26. A non-transitory computer readable storage medium having stored thereon computer readable instructions that, when executed at a computer system, cause the computer system to perform the method as claimed in any of claims 1 to 23.

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