Dynamic control algorithm and program for power-assisted lift device

• US 6,204,619 B1
• Filed: 10/04/1999
• Issued: 03/20/2001
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Oriet, Leo Paul Gerard, Gu, Edward Y. L.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/412,188
• Time in Patent Office: 533 Days
• Field of Search: 318/567, 318/568.1, 318/568.11, 318/568.2, 318/568.21, 318/568.22, 318/646, 254/1, 254/33, 254/45, 254/264, 901/50
• US Class Current: 318/568.11
• CPC Class Codes: B66C 23/005 with balanced jib, e.g. pantograph arrangement, the jib being moved manually

Abstract

A dynamic control system for a power-assist device has a statics formulator for determining a set of static torques for the lift system based on force data from the lift system. The control system further includes a dynamics formulator for determining a set of dynamic torques for the lift system based on joint data and the static torques. A static torque and a dynamic torque is therefore determined for each joint of the assist device. The control system also includes a torque summation module for summing the dynamic torques with the static torques to determine torque data for each joint of the lift system. The torque summation module applies the torque data to the lift system to achieve dynamic compensation within a substantially shorter response time. Thus, a method and system are presented for dynamically controlling a power-assisted lift system to continuously reduce human operator strain in a real-time mode.

Claims

1. A dynamic control system for continuously reducing strain on a human operator of a power-assisted lift system, the lift system having a plurality of joints, said control system comprising:

a statics formulator for determining a set of static torques for said lift system based on force data and joint data from said lift system;

a dynamics formulator for determining a set of dynamic torques for said lift system based on said joint data and said static torques; and

a torque summation module for summing said dynamic torques with said static torques to determine torque data for each joint of said lift system, said lift system using said torque data to control each joint of said lift system such that strain is reduced on the human operator.

2. The control system of claim 1 wherein said joint data comprises joint position, joint velocity, and joint acceleration for each joint in said lift system.

3. The control system of claim 1 wherein said dynamics formulator comprises:

an inertial matrix module for modeling an inertial matrix of said lift system;

a partial differential inertial matrix module for modeling a partial differential inertial matrix of the lift system; and

a dynamic torque calculator for calculating said dynamic torques from said joint data, said inertial matrix, and said partial differential inertial matrix.

4. The control system of claim 3 wherein said inertial matrix module models said inertial matrix based on joint position data and compensated static torques.

5. The control system of claim 3 wherein said partial differential inertial matrix module models said partial differential inertial matrix based on joint position data and joint velocity data.

6. The control system of claim 1 wherein said statics formulator comprises:

a Jacobian matrix module for modeling a Jacobian matrix for said lift system;

a compensator module for adapting an inertial matrix and the Jacobian matrix; and

a static torque calculator for calculating said static torques from said Jacobian matrix and said force data.

7. A power-assisted lift system comprising:

a power-assist device for assisting a human operator in manipulating objects, said assist device generating joint data;

a sensing module for converting a force into force data, said force applied to said power-assist device by said human operator; and

a dynamic control system for continuously reducing operator strain in a real-time mode based on said force data and said joint data.

8. The lift system of claim 7 wherein said dynamic control system comprises:

a statics formulator for determining a set of static torques for said assist device based on said force data and said joint data;

a dynamics formulator for determining a set of dynamic torques for said assist device based on said joint data and said static torques; and

a torque summation module for summing said dynamic torques with said static torques to determine torque data for each joint of said assist device, said lift system using said torque data to continuously reduce strain on said human operator in a real-time mode.

9. The lift system of claim 7 wherein said assist device includes a joint data module and said joint data comprises joint position, joint velocity, and joint acceleration for each joint in said assist device.

10. The lift system of claim 9 wherein said joint data module calculates said joint acceleration based on said joint velocity and a partial derivative inertial matrix for said lift system.

11. The lift system of claim 10 wherein said joint data module includes a joint encoder and a tachometer at each joint of said assist device.

12. The lift system of claim 7 wherein said assist device comprises:

a joint-servo controller for converting joint torque data from said dynamic control system into motor control data;

a plurality of joints; and

a servo motor manipulating each said joint based on said motor control data.

13. The lift system of claim 7 wherein said sensing module comprises a six-axis force sensor coupled to a steering handle of said lift system.

14. A computer implemented method for controlling a power-assist device, the assist device having a plurality of joints, the method comprising the steps of:

retrieving force data from said assist device, said force data resulting from human operation of said assist device;

retrieving joint data from said assist device; and

compensating said human operation of said assist device based on said force data and said joint data.

15. The method of claim 14 further comprising the steps of:

determining a set of static torques for said assist device based on said force data and said joint data of said assist device;

determining a set of dynamic torques for said assist device based on said static torques and said joint data;

generating torque data from said dynamic torques and said static torques; and

applying said torque data to each said joint of said assist device.

16. The method of claim 15 further comprising the steps of:

measuring a joint position for each joint of said assist device;

measuring a joint velocity for each joint of said assist device;

computing a joint acceleration for each joint of said assist device; and

calculating said dynamic torques from said static torques, joint positions, joint velocities, and joint accelerations.

17. The method of claim 16 further comprising the steps of:

modeling an inertial matrix based on compensated static torques; and

modeling a partial differential inertial matrix based on said joint positions and joint velocities of said assist device.

18. The method of claim 17 wherein the joint accelerations are computed from the joint velocities and the partial differential inertial matrix.

19. The method of claim 15 further comprising the steps of:

formulating a Jacobian matrix for said assist device;

transposing said Jacobian matrix into a transposed Jacobian matrix; and

multiplying said transposed Jacobian matrix by said force data.

20. The method of claim 19 wherein the Jacobian matrix is based on a joint position vector.