| Abstract |
In several applications using small power actuators, a good dynamic and steady state position accuracy is needed, at low speeds and with limited accelerations (scientific instruments, special machine-tools and robots). For these applications stepper motors are commonly used. The aim of our study was to develop a digital synchronous torquer and test it as a challenger of stepper motors coupled to the load through a gear reducer. The synchronous motor is coupled with only one sensor which is generally a resolver, in some cases however other sensors might be used wjth the same performances: the digital system is designed to get such a flexibility. We tested a resolver and a capacitive encoder, which use is compulsory when power djssipation must be mjnjmjzed: spatial applications for example (JL. SABRIE and others,1986; M. GORISSE and others,1986). In all cases a high chopping frequency inverter has been chosen to supply the motor and the torque control is realized by analog current control loops. The digital circuits, mainly the 8086 microcomputer, are dedicated to the autopiloting, the position control, and the treatment of the sensor signals which may be very important with some sensors (that was the case with the capacitive encoder). This paper describes more specifically the control system hardware and software; it compares the results that are got with the conventional resolver and with the capacitive encoder; the equivalent stepper motor performances are approached. |
