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Figure 8.2, Simulink model with motor shaft position in radians as input and gives the actual motor shaft position out in
radians. Between the reference and actual value of the motor shaft position the SERCOS bus and one MC-4 connected
to one motor is shown. Also the Encoder which measures the motor shaft position is simulated a SinCos Encoder.
8.1 MC-4
The MC-4 is the servo amplifier that is used to control the motor shaft position. For the Delta-3
robot one can consider Figure 4.9 where the three MC-4 drives controls shaft position i
(i=1,2,3) corresponding to the single-input/single-output system of the decoupled and linear
part. The model of one MC-4 and one motor is shown in Figure 8.2. The SERCOS bus is
simulated as a delay of the cycle time, which is 1ms for the Delta-3 robot simulation. Before
the SERCOS bus there is a gain which increments the input signal with 2 19 .
As shown in Figure 8.2, a cascade controller is used in the MC-4. The cascade controller is
build up by one outer loop which controls the shaft position with a P-controller and two inner
loops which controls the velocity and the acceleration, respectively. In the two inner loops PIcontrollers
are used to reduce the steady state error. Also position, velocity and current
feedforward compensation is added to reduce the tracking error.
8.2 MOTOR
The motors that are used to actuate the Delta-3 robot arms are ELAU GmbH motors. The motor
type is AC synchronous motors which are modelled in the simulink model as shown in Figure
8.3. To get more information how to derive a motor model in Simulink, see (16 pp. 7-24).
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Public Report ELAU GmbH, Marktheidenfeld
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