Michel Doyon

Adaptive Control of Harmonic Drives

Aimed at achieving ultrahigh control performance/or high-end applications of harmonic drives, an adaptive control algorithm using additional sensing, namely, the joint and motor positions and the joint torque, and their practically available time derivatives, is proposed. The proposed adaptive controller compensates the large friction associated with harmonic drives, while incorporating the dynamics offlexspline. The L 2 /L∞ stability and the L 2 gain-induced H ∞ stability are guaranteed in both joint torque and joint position control modes. Conditions for achieving asymptotic stability are also given. The proposed joint controller can be efficiently incorporated into any robot motion control system based on either its torque control interface or the virtual decomposition control approach. Experimental results demonstrated in both the time and frequency domains confirm the superior control performance achieved not only in individual joint motion, but also in coordinated motion of an entire robot manipulator.

Adaptive control of harmonic drives

In this paper, an adaptive control algorithm is designed for controlling the harmonic drives used to drive robot manipulators. Direct torque measurement is available by using the flexspline mounted strain-gauges. The torque error is added to the required velocity. Adaptive friction compensation and flexspline dynamics based control are the two main contributions in the paper. The L/sub 2//L/sub /spl infin// stability and the L/sub 2/-gain induced H/sub /spl infin// stability are guaranteed in both joint torque and joint position control modes. Experiments conducted on two typical types of harmonic drives confirm the feasibility of the controller in both time and frequency domains. By using the virtual decomposition control approach, the independently designed joint adaptive controller for harmonic drives can be efficiently incorporated into the motion/force control systems of robot manipulators.

Adaptive Control of Harmonic Drives Based on Virtual Decomposition

Harmonic drives are interesting for robotic applications due to their attractive properties such as high reduction ratio, compact size, low mass, and coaxial assembly. However, the high friction and the dynamics of the flexspline are the main issues that significantly challenge the control systems. In this paper, an adaptive controller capable of adaptively compensating the friction, while incorporating the dynamics of the flexspline, is developed in both joint torque and joint-position control modes. The virtual decomposition control approach allows the dynamics of harmonic drives to be controlled separately from the conventional dynamics of the robots. Adaptive friction compensation and flexspline dynamics based control are the two main contributions of this paper. The L2/Linfin stability and the L 2-gain-induced Hinfin stability are guaranteed. Experimental results demonstrated in both time and frequency domains confirm the feasibility of the proposed approach

Dynamic Emulation of Space Robot in One-g Environment using Hardware-in-the-Loop Simulation

To verify all robotic tasks involving a space robot interacting with environment, such as the Special Purpose Dexterous Manipulator (SPDM), one should appeal to a simulation technique because the space robot cannot operate in an 1-g environment. However, to simulate dynamical behavior of a robot interacting with environment creates difficulties due to complexity of the physical phenomenon involved during the interaction. In this work we develop an hardware-in-loop simulation (HLS) technique, where a simulation of the space robot dynamics is combined with emulation of the contact dynamics by using a rigid robot prototype performing contact task. The rigid robot is not dynamically or kinematically equivalent to the space robot, but it is controlled so that its endpoint dynamics replicates that of the space robot. Simulation and experimental results given from implementation on a six degrees of freedom manipulator are presented.

Control System Prototyping of the STVF Manipulator Test-Bed

Abstract Through its implication on the International Space Station (ISS), Canada is responsible for the verification of all robotic tasks involving the SPDM. To this end, the Canadian Space Agency is building the SPDM Task Verification Test-bed (STVF). Risks associated with the proposed concept have been identified, particularly in the area of control systems, dynamic behaviour and contact stability of the STVF Manipulator Test-bed (SMT). To mitigate these risks, a one degree-of-freedom prototype is implemented to validate the proposed control system architecture. The results are presented and discussed in light of the final SMT implementation.

An experiment on skill degradation and recovery for safe MSS operations

Summary form only given. SMP is a research project to study how skills degrade and recovery. The operation of the wide variety of manned and unmanned space vehicles and their associated supporting docking and robotics systems calls for demanding training of crews both on ground and on orbit. Crew must achieve and maintain proficiency in these complex skills. Failure to maintain critical skill proficiency places the lives of the crew and the various space assets at significant risk. Canada has a significant investment in space activity via our contribution of Astronauts and robotics hardware and software. Skills degrade over time and the frequency and depth of proficiency and refresher training to keep crew proficient needs to be studied. A numbers of factors are known to affect the crew on-board performance: psychological and physiological stress factors of the space flights, pre-flight training program fidelity, skill degradation, man-machine compatibility, etc. An on-board system capable of correcting and compensating for these factors would be required to decrease probability of potential crew error. This point is even stronger in the case of manned space exploration. Currently Canada has technology on orbit in the Russian Segment of the International Space Station to conduct experiments tracking the status of crew degradation in ability to perform tasks essential to the operation of complex space vehicle equipment. This research project looks at studying performance degradation and skills recovery as it applies to complex psycho-motor and mental activity. The long-term goal of this research project is to gather data to help determine the frequency of on orbit training and/or the approach to onboard training to ensure that complex systems are operated safely. This project is ongoing since 2003, we have sent H/W in space twice already. This presentation will address the technological challenges required to build a simulator and associated analysis tool software able to run on a stand alone computer. It will also present preliminary results and experimental setup onboard the International Space Station