Hi All - The issue with cnc machine control is that there are three main domains to control. rapids ie no tool load, roughing and finishing. Each domain has a different inertial condition, so you can't use a simple one set up PID to cover all the bases. The h-infinity algorithms use an optimisation map to cover all the bases. Quadrature is a numerical calculation method that uses a few points to calculate the functions vs starting with the continuous function. It is faster to calculate and accurate enough for the CNC application vs creating the continuous curve then differentiating etc then looping back to the velocity. So starting to get a grip on how these guys are doing this... Peter

Engineering jerk for our purposes has no physical symptom or existential affect. Jerk is calculated to establish how smooth the acceleration is and to identify where acceleration peaks occur. Acceleration produces inertial forces on masses (F=ma) and "jerky" motion is created as a function of machine compliance, inertial loads and actual loads (called body loads). These systems smooth the velocity (S-curve) to smooth the accelerations but leave peaks in jerk. But these peaks are much lower then when using a trapezoidal velocity profile.