The Research On Modular Manipulator Motion Control Based On DC Servo Motors

Compared with conventional manipulator, the modular manipulator has advantages of ashort development cycle, a large scope of work, easy maintenance and it has become a researchfocus at home and aboard. The modular manipulator involved in this paper has six degrees offreedom and uses DC servo motors as its joints’ power equipment. The manipulator’s grabbingor moving along the desired trajectory is achieved relying on the cooperation with each otherof the six joint’s motors. If the position servo control’s accuracy of each motor is improved, themotion state of the manipulator is better controlled and the manipulator can track the desiredtrajectory more effectively. At present, domestic research work focuses on the modularmanipulator’s hardware design, software design and algorithm simulation, but relatively few toimprove the accuracy of a single motor’s position servo control. In this paper, through theactual debugging of the motor, a high-precision position servo control method is designed. Thepaper’s main work is:1. The current situation of the domestic and international research on modular manipulatoris analyzed and motion control problem’s key issues and its solution are described. Modulardesign, control system, PID algorithm, the CAN bus, DC motor, PWM principle and digitalsignal processor are introduced.2. According to modular manipulator’s joints, system’s hardware is designed and itssoftware is compiled and tested to verify its validity. Motor’s control functions of speed servoposition servo are achieved. The drive device of the system consists of TI company’sTMS320LF2407DSP controller and some of peripheral circuits. The joint module’s powerequipment is DC servo motor.3. A problem of tracking to specified location within50milliseconds is put forward inorder to ensure the smooth and operating accuracy of modular manipulator when it is runningalong a specified trajectory.A phenomenon is found through experiments: Under the samesystem, if the PID parameters are the same, the rise time of it is the same no matter what kindof step signal it is, and the curve approximates a straight line during this time; And further,under the same system, if the PID parameters are the same, the transition time of it is the sameno matter what kind of piecewise constant signal it is, and the curve approximates a straightline during this time.4. A set of high-precision position servo control method is designed according to theexperimental phenomena above. A speed controllable time zone is found within the regulationtime of the PID control algorithm, thus effective control of the speed is achieved. It is provedby the actual motor debugging that the program designed is able to precisely control motor’sspeed and position at the same time within fifty milliseconds. The speed changes smoothly andis consistent with the ideal speed’s curve. The desired objectives are achieved. Because of themanipulator’s modular design, high-quality programs could be ported to other equipment, thusthe cost and development are reduced.