Some early industrial robots, especially the larger variety, were often powered by hydraulic systems, and some smaller robots used stepper motors to achieve drive. Hydraulically powered robots had significant limitations in accuracy and repeatability, plus they were relatively slow, which limited the range of tasks to which they could be applied. Further drawbacks were the noise from the hydraulic powerpacks and the fact that they were not suited to applications within clean environments.
Today hydraulic power for industrial robots has been superseded by electric drive systems. The stepper motor systems used to power some of the smaller early robots also had their limitations, and certainly for mainstream industrial robots. These have now also been replaced with servo motors.
Modern servo motors offer a wide range of advantages over stepper motors including:
- Their ability to move higher payloads
- They offer much better repeatability due to their closed loop feedback
- They can operate at much higher speeds
- Servo motors do not require to be re-homed following e-stop conditions
- Servo motors allow better optimisation of operating parameters
There are also Linear Motors and Direct Drive Motors available which are ideally suited to certain cartesian type applications. These types of motors offer numerous advantages. They eliminate the belts, pulley, racks and pinions or other mechanisms needed to translate rotary motion into linear motion. This type of motor also eliminates the need for additional items such as gearboxes or drive couplings. Overall, this type of motor requires less maintenance over its working life.