Inject More Voltage, Power into AC Motor Drives for Industrial Robots (.PDF Download)

Greater use of robots in the world of automation is bringing about higher productivity in manufacturing, as well as lowering costs. To meet those objectives, robots must have faster response times as well as higher precision in positioning—and that means improvements in motor-drive control. 

Motors inside the robot supply variable speed and torque at precise points. The robot’s controller coordinates the motion along different axes for exact positioning. These movements must be done with great power efficiency. 

Two three-phase motor-driver inverter designs have surfaced that can produce the required level of performance. These designs consist of high-end power supplies, intelligent motor drivers, high-performance control signal processing, and intelligent sensing that all function together to deliver the precise speed and torque needed instantaneously by robots. 

Motor Control with AC Drives

The larger industrial-strength robots utilize three-phase ac motors to move its joints. These motors require special driving circuitry to deliver the precise control necessary for precision real-time operation. The figure shows one example.

The drive electronics usually consists of a high-voltage ac-dc supply incorporating a three-phase rectifier that delivers dc to a pulse-width-modulated (PWM) inverter usually made up of IGBTs. The IGBTs deliver pulses to the three motor windings to produce the desired drive frequency.