There are three vital “organs” that every useful robot needs: the senses for vision, hearing and touch; a “brain” that computes a response to sensory stimuli and “muscles” that deliver the mechanical response. Sensors and computers continue to gain in capabilities, even as they get cheaper and easier to use – increasingly they are modular and “plug and play.” But, to be useful, a robot must move and harnessing the appropriate motive power can be challenging. Electromechanical design requires some engineering.
Selecting the right motor is a non-trivial exercise: It starts with specifying performance minima and maxima. These apply to motor speed, acceleration, torque as a function of speed, among others. Precision and repeatability limits are important considerations. Then, of course, there are the more obvious physical parameters – size, weight and cost.
Unless you’re building an industrial robot to assemble cars or handle large payloads, the most common choices for motive power are DC motors. These can range from the humble brushed DC motors, to the more complicated brushless and stepper motors that rely on complex electronic controls to operate.
Luckily, an eminently readable article on robot motor basics from Mouser, the distributor, has come to the rescue. It is a step-by-step guide that explores tradeoffs around the ability to manage torque, precise positioning, reliability, maintenance considerations, electrical noise generation, cost, etc.
It delves into selection criteria for the control electronics, including for the power transistors that provide current to the motor and for the all-important controller. What type of controller is right? Controllers can be built around general-purpose programmable processors, or computation-friendly FPGAs, or based on dedicated control ICs from specialized motion-control vendors. The controller can be the single most important choice in the design, and that choice needs to be made before selecting a specific vendor.
As motors and control mechanisms improve – dramatically in some capabilities — many applications that previously used hydraulics are switching over. For new designs, especially in small-to-medium robotic situations (and even many of the larger ones), the first choice is to go with electronic controls and electric motors.
Get ahead of the curve here