Actuator position control with signal sensing

An actuator position control system for brush-type DC motors. The system includes a sensor, amplifier or differentiator, central control unit (microprocessor), and motor driver. The system utilizes the differential signal di/dt to indicate the falling edges of commutation spikes in the motor current profile. In a first embodiment, an inductor is selected as the signal sensor, because voltage drops across the inductor are directly proportional to di/dt. The voltage drop, L(di/dt), across the inductive sensor is input to the amplifier, amplified, and then sent to the microprocessor. In a second embodiment, a sensing resistor and a differentiator are substituted for the inductive sensor and amplifier, respectively. The microprocessor reads the output pulses from the amplifier or differentiator and compares the pulse count to an input command signal. The microprocessor then sends shaft position control information to the motor driver.