Position-Posture Control of a Planar Four-Link Underactuated Manipulator Based on Genetic Algorithm

This paper presents a position-posture control strategy based on genetic algorithm (GA) for a planar four-link passive-active-active-active (PAAA) underactuated manipulator. The control objective of the system is to move the end effector from any initial position to any target position with a specified posture. First, the integrability of the PAAA manipulator is analyzed based on its dynamic model. Then, the control process is divided into three stages based on the partial integrability of a PAAA system and the complete integrability of an Acrobot system. In each stage, the system is reduced to be an Acrobot-like system, and an angle constraint between an actuated joint and the unactuated one is derived based on the complete integrability of an Acrobot system. Next, a mathematical optimization model is constructed to solve the target angles based on multiconstraints and the control objective. And GA is applied to obtain the target angles. Finally, the controllers are designed for each stage to move one actuated joint to the target angle in turn. Simulation results demonstrate the effectiveness of the proposed control approach.