05-05-2011, 03:02 PM
Abstract
In this paper a motion control system of a robot arm isdescribed. Robots arms are built their motion machine, Motors. DCmotor is chosen for the robot arm and the author also presents how tochoose this motor. The robot arm is with single degree of freedomand motion control system for it is selected using MATLABSimulink software. This paper is mainly focus to apply MATLABsoftware to Control system design. The system is simple but it isdeigned the motor to move the robot arm to proper angular positionaccording to the input.Keywords—Control system, DC motor, MATLAB Simulinksoftware, robot arm.
I. INTRODUCTION
mOTION control is one of the technological foundationsof industrial automation. Whether the motion of aproduct, the path of a cutting tool, the motion of an industrialrobot arm conducting seam welding, the motion of a parcelbeing moved from a storage bin to a loading dock by ashipping cart, or another application, the control of motion is afundamental concern. Putting an object in the correct placewith the right amount of force and torque at the right time isessential for efficient manufacturing operation.To be able to control a motion process, the precise positionof objects needs to be measurable. Feedback comparison ofthe target and actual positions is then a natural step inimplementing a motion control system. This comparisongenerates an error signal that may be used to correct thesystem, thus yielding repeatable and accurate results.However, the use of feedback can lead to an unstable systemwhose output may oscillate or even go to infinity with a smallinput signal. Stability determination is therefore an importantdesign consideration. One specification for absolute stabilityrequires that the poles of the transfer function must be in theleft half of the s-plane. Absolute stability, often specified inthe frequency domain, is essential and necessary but notsufficient. Frequency domain specifications relating to relativesystem stability may also be given. For relative stability, certain phase margin and gain margin may be specified toensure that the system will remain stable although someparameters change due to temperature changes, aging orother environmental changes. If a system is stable, then otherperformance criteria, specified in either the time or frequencydomain, may be considered to meet the performancerequirements. Short-term, or transient, response specificationssuch as rise-time or percent overshoot to a unit step functioninput may be given. Fortunately, the advance controlcalculation can be solved with the help of using Matlabsoftware.
II. CHOOSING A DCMOTORA DC
motor with armature control and a fixed field isassumed. The electrical model of such a DC motor is shown inFig. 1. The armature voltage, ea(t) is the voltage supplied byan amplifier to control the motor. The motor has a resistanceRa , inductance La and back electromotive force constant, Kb.The back emf voltage, vb(t) is induced by the rotation of thearmature windings in the fixed magnetic field. The counteremf is proportional to the speed of the motor with the fieldstrength fixed
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