Estimation of Motor Startup Speed Profile Using Low-Resolution Timing Signals and Motor Speed-Torque Curve

Motor startup speed profile of motor rotational speed versus rotational angle can often be very useful during product developments, such as for detailed kinematic or dynamic component analyses. In compressor tests, a sensor, usually a proximity probe or an optical pickup, is commonly used to generate low-resolution timing signals. The lowresolution timing signals are sufficient to detect the angular position of crankshaft for stable operating conditions. However, the low-resolution timing signals can not be directly used to estimate the motor startup speed profile. A numerical calculation method is thus developed to estimate the motor startup speed profile from the low-resolution timing signals and the motor speed-torque curve (or torque-speed curve). An iterative numerical solution procedure using the explicit finite-difference method that employs a time marching algorithm to integrate the differential equations over time is presented in this paper. The finite-difference calculations marches the solutions in time. The solutions calculated by the finite difference method are iterated to estimate the mass moment of inertia according to the low-resolution timing signals. The numerical calculation method described in this paper can also be used to predict other motor dynamic behaviors of a motor-load system.