Design and Control of Under-Actuated and Over-Actuated Mechanical Systems - Challenges of Mechanics and Mechatronics

摘要

The majority of current mechanical systems used in machinery and especially those which arc controlled by microprocessors can be described as equal-actuated. This means that the number of actuators (drives, controls) is equal to the number of degrees-of-freedom. The mechanical systems can have directly such property or it can be as such treated during the design and operation. Classical rigid mechanisms can have such property naturally. Generally all flexible mechanisms violate this property as not all flexible degrees-of-freedom can be actuated and thus directly controlled. However, there are important mechanical systems which does not fulfilled this criterion of equality of actuators and degrees-of-freedom. The examples of under-actuated systems are bio-mechanical systems during dynamic phase of motion, technical systems of cranes, vehicles, underwater robots, missiles with failed engines, inverted pendulum, ball on the beam. The examples of over-actuated systems are again biomechanical systems during the contact with ground and recently introduced redundantly actuated parallel robots. The paper first deals with the introduction and definition of the property of under-actuation, equal-actuation and over-actuation. Then the paper deals with the control of under-actuated or over-actuated systems and the challenge how to design such systems.