Why are linear motors not used to actuate robots?
While linear motors are highly capable and offer several advantages, there are several reasons why they might not be the first choice for actuating robots in all cases:
Cost and Complexity
Linear motors are generally more expensive and complex compared to other types of actuators, such as traditional linear actuators or stepper motor linear actuators. The high cost, particularly due to the use of rare-earth magnets, can be a significant barrier for many applications34.
Environmental and Interference Issues
Linear motors can generate strong magnetic fields that can interfere with surrounding electronic devices or components, which is a concern in environments sensitive to magnetic fields, such as in MRI machines or metal cutting applications34.
Heat Generation and Cooling
Linear motors, especially those operating at high cycle rates and extreme acceleration profiles, generate a significant amount of heat. This requires additional cooling systems, such as air or liquid cooling, to manage the thermal limits, adding complexity and cost5.
Mechanical Considerations
In multi-axis applications, the moving mass of one linear motor axis can become part of the payload of another axis, significantly increasing the power requirements and complicating the system design. Additionally, linear motors require careful consideration of bearing systems to maintain the necessary air gap and ensure smooth operation5.
Cable Management and Stroke Length
Linear motors have limitations related to stroke length and cable management. The need to energize the forcer along the full stroke length can be challenging and expensive, especially with high-flex cables and raceways. This can be a point of failure and adds to the overall complexity of the system3.
Alternative Options
For many robotic applications, traditional linear actuators (such as ballscrews, belt drives, and rack-and-pinion systems) or stepper motor linear actuators may offer sufficient performance at a lower cost and complexity. These alternatives can be more economical and still meet the precision and speed requirements of many robotic tasks23.