Drive technology is demanded especially with mobile robots. The most important features are shown from torque to installation space at a glance.
High power density
DC motors are such examples for ironless Maxon motors with and without brushes. A high degree of efficiency is characterized by fast rotating motors that are usually long and narrow and the torque is rather low. In robotics, high torques are achieved that are combined with gearboxes. The high force with a linear movement is required with an appropriately designed mechanism with a high reduction ratio that can still be exploited with the advantage of high-speed motors. Spindles with small pitches or rollers and small diameters wheels are some examples.
The increase of a number of magnetic poles is achieved by higher torques. 4-pole Maxon’s EC motors are the first step. Multi-pole brushless DC motors are designed often with a grooved iron core but at a higher torque and lower speed, power is delivered.
The force is generated with flat motors with an external rotor at the greatest possible distance from the rotation axis with resulting in a comparatively high torque density. Although the inertia of the rotor’s moment of inertia is high, dynamics is limited. Brushless EC flat motors can be cost-effectively manufactured due to conventional multi-tooth winding with an iron core and the use of an isotropic permanent magnet right is magnetized in one step. Multi-pole internal rotors are EC-I motors that are in addition to the high torque resulting in low mass inertia. As a result, motors are extremely dynamic and got a small mechanical time constant that is sometimes less than one millisecond.
High pole count, but expensive
Motors with a high number of poles are an example of torque motors that are slowly rotating and high-torque electric motors with hollow shaft. Most often they are frameless as it consists of only rotor and stator, designed into an application. Gears, belts, coupling, or bearing are such elements that can be saved with backlash-free direct drives that are typically used in dynamic applications with rigid control. Linear drives can be considered a special case.
High switching frequencies are required by torque motors due to many poles. Water cooling helps to dissipate the generated heat. The torque and the dynamic requirements of mobile robotics applications are perfectly met by the torque motors. The lack of standardization with necessary design integration can make use of cost-intensive. Therefore, robots are preferred with modular flexible motor-gearbox combinations with the motor type and specific requirements that are design based on performance, installation space, and cost if not it is forgotten.