Question 10.3.7: Controlling the Speed of a Conveyor A conveyor drive system ...
Controlling the Speed of a Conveyor
A conveyor drive system to produce translation of the load is shown in Figure 10.3.11. To translate the load a specified distance, the drive wheels must rotate through a required angle, and this can be accomplished by controlling the speed, often with a trapezoidal speed profile. The equivalent inertia of the load and all the drive components felt at the motor shaft is I_{e}. The effect of Coulomb friction in the system produces an opposing torque T_{Fe} at the motor shaft, and the damping in the system is negligible. Develop the block diagram of a proportional control system using an armature-controlled motor for this application. Assume that the drive wheel speed ω_{L} is measured by a tachometer and that the motor speed ω_{m} is related to the drive wheel speed by ω_{m} = N ω_{L} , where N is the speed ratio due to the reducer and the chain drive.
The dynamics of the mechanical subsystem are described by
I_{e} \frac{d ω_{m}}{d t} = T − T_{Fe} (1)
where the motor torque is T = K_{T} i_{a} . The system is like that shown in Figure 10.3.4. The block diagram can be obtained by modifying Figure 10.3.8 using equation (1) and collecting the various gains into one gain: K_{P} = K_{tach} K_{1} K_{a}. The resulting diagram is shown in Figure 10.3.12.
