Zhi-Wei Luo

Control design of robot for compliant manipulation on dynamic environments

The problem of designing the control for a robot that performs compliant manipulation on dynamic environments is studied. Compliant manipulation requires the controlled robot not only to follow the input trajectory exactly in free motion space, but also to manipulate adaptively on dynamic environments while making compliant contact with the environments dynamic constrained space. An original model matching control approach for the control design is presented. The problems of selecting a reference model according to the environmental dynamics, its dynamic model uncertainty, the contact discontinuity and the robot actuators output limitation are studied. The problem of how to implement such a reference model in a robots control system is considered. In addition, adaptive algorithm for the robot manipulator are given to improve its performance when imposing compliant manipulation on a dynamic environment with parameter uncertainties. The effectiveness of this approach compared to the impedance control approach is illustrated through computer simulations and experiments. >

Multiple robot manipulators' cooperative compliant manipulation on dynamical environments

This paper discusses compliant manipulation of multiple robot manipulators cooperative in a dynamical environment. Cooperative compliant manipulation requires the simultaneous control of both the objects position and the interaction forces between the robots and the object. It is shown that position-controlled manipulators can not perform this kind of task successfully. It is proved that, in order to avoid excessive pressing, the frequency bandwidth of the overall control systems including the manipulators and the object should be adjusted according to the object dynamics. A unified model-matching control approach is developed in which each autonomous robot uses its own position and interaction force information to adjust the systems frequency bandwidth and to maintain the internal force in a desired performance. The reference models of the objects position and the internal force are selected with respect to the objects dynamics, and the force feedback controllers are designed accordingly to realize the reference models. Simulation studies show the effectiveness of this control approach.

Development of artificial muscle actuator using ionic polymer with its application to biped walking robots

We are developing an artificial muscle linear actuator using ionic polymer-metal composites (IPMC) which is an electro-active polymer that bends in response to electric stimuli and the goal of our study is to apply the actuator to robotic applications especially to a biped walking robot. In this paper, we will describe the structure of the actuator and an empirical model of the actuator which has two inputs and one output, and whose parameters are identified from input-output data. Based on the empirical model, we demonstrate walking simulations of a small-sized biped walking robot. In the numerical simulation we assume that the developed actuators are connected both in series and in parallel to a joint of the walking robot so that the actuators supply enough torque to the robot and that they are stretched and compressed enough. It is shown throughout the simulation that the biped walking robot with the actuators can walk on a level ground with a period synchronized with a period of input signal.

Compliance control of an ultrasonic motor powered prosthetic forearm

The capability of a prosthetic device to mimic the response of the actual limb with respect to voluntary motor commands and to environmental loads should be addressed. This paper discusses the compliance control of an ultrasonic motor powered prosthetic forearm which utilizes cutaneously measured electromyogram (EMG) signals sensed with electrodes over the muscles as means of detecting motor commands sent by the central nervous system (CNS). Compliance control of the artificial limb was studied by implementing the bilinear model of the forearm and hand. This model emphasizes the role of the visco-elastic properties of the musculo-skeletal system of the actual limb in controlling its net configuration and movement. The flexor and extensor muscles extending over a joint influence the overall joint impedance and determines the equilibrium position of the joint. Relaxing both flexor and extensor muscles makes the joint compliant to external forces, while activating both muscles increases the impedance of the joint.<<ETX>>

Compliance Control of Direct Drive Manipulator Using Ultrasonic Motor

A compact size light weight direct drive(DD) manipulator with traveling wave ultrasonic motors (USMs) as actuators was developed. Contact tasks1) were realized by adapting an adjustable compliance control system of the USM. In the system, a torque feedback control by interaction force to environment is not used. Experiments on contact tasks like crank rotation and cooperative motion of two manipulators were observed.

Chapter 13:Phenomenon of Spatially Growing Wave of a Snake-like Robot: Natural Generation of Bio-mimetic Swimming Motion

In the swimming of an underwater snake robot made of an ionic polymer metal composite (IPMC), the bending wave of the snake robot grows from the head to the tail even if a uniform moment (or voltage) with constant amplitude is applied. This interesting phenomenon is also observed in the swimming of living fish and is thought to contribute to energy-efficient swimming. The phenomenon observed in the swimming of the robot may suggest a hypothesis such that living fish utilize the elasticity of their musculoskeletal systems when they swim. That is to say, the growing wave phenomenon of living fish may be generated unintentionally and naturally. This chapter introduces a modelling and analytical solution to the bending deformation of a beam-shaped IPMC robot. The obtained analytical solution can simulate the envelope of the deformation shape, which increases from the head to the tail. In the experiment, the growing wave phenomenon of the robot is measured by a video camera. From the captured deformation data, the parameters of the analytical model are estimated. Finally it is shown that the deformation shape of the analytical model well predicts the experimental deformation.