A computer controlled dynamometer I was commissioned to design a number of years ago. The dynamometer was created to test the permanent magnet electric motors used in radio controlled model car racing. We sold a number of the devices to racing teams around the world, including one to a major motor manufacturer in Japan.The Dyno works by making the motor accelerate a flywheel from standstill. Every half revolution of the flywheel is timed in microseconds. From these timings the speed and acceleration of the fywheel are calculated and thus the torque and power being generated by the motor. The voltage applied to and the current drawn by the motor are also measured.
Screen shot showing the results of applying a line-fitting algorithm to the timing data to calculate the acceleration of the flywheel. I used a little machine code routine first to smooth out the noise in the timing data.