Driving precision in robotic motors

ROBOTS ARE no longer confined to the assembly lines of the automotive sector. Today, they’re operating in surgical fields, warehouses, agricultural sectors and even homes. As robotic systems become more specialised and integrated into diverse environments, the demands placed on their core components have grown too.

Robotics requires precise, fast and dynamic motion. Motors are required to provide high torque, run with good reliability over extended duty cycles and easily interface with sensing and control systems. Other limits, such as low noise and weight, apply when the motor is located within a mobile or collaborative robot.

Motor selection and key considerations

There is no one-size-fits-all when it comes to motors. The choice depends on what the motor will do, whether that’s handling a surgical instrument with sub-millimetre precision or powering an articulated arm in a factory. 

Brushless DC motors are likely to be the preferred choice in most robotic applications given that they are efficient, durable and require little maintenance. They are lightweight but can provide smooth and controlled movement, making brushless motors the best choice for dynamic operation where precision and reliability are a priority. 

Stepper motors offer true open loop positioning while being a cost-efficient option for less complex robotic operations, such as small pick-and-place systems or light-duty automated devices, where high torque variation or speed isn't as important. However, they fall short in operations demanding dynamic response and continuous movement, as their stepwise motion can limit smooth acceleration and precision at higher speeds. 

For confined spaces or where weight is a consideration, coreless motor or flat motor designs are a sensible choice. They have an excellent power-to-size ratio, making them ideal for miniature robotic joints, mobile devices, or any application where compact, lightweight components are critical without sacrificing performance.

Choosing the right motor begins with understanding key technical specifications. Speed must allow smooth acceleration and braking for repeatable motion, while size and weight are critical where space is limited. Duty cycle must also be considered, as thermal performance affects reliability and motor life.

Control, feedback and integration

A motor is not a standalone device; its operation is contingent upon the feedback and control systems to which it’s being matched. Closed-loop control, through resolvers or encoders, gives robots the precision and responsiveness they are required to possess. Encoders of high resolution allow the position and speed information that are critical to let the controller make real-time adjustments.

Integrated motors, motors with onboard drivers and encoders, simplify system design and reduce footprint, which is especially worth the cost in space-constrained robotics applications. They can also increase reliability by reducing wiring and connection points.

In choosing motors, engineers must consider how feedback and control features track the motion profile and accuracy requirements of the robot. Selecting a motor with versatile integration skills allows engineers to expand and upgrade in the future, maintaining systems flexible as technology continues to advance.

Surgical robotics

Robotic surgery makes some of the most demanding challenges for motor technology. Surgical use requires motors to be accurate, compact, quiet and capable of delivering smooth high-speed motion. Space constraints in surgical tools are often critical, making ultra-flat brushless DC motors a natural fit.

A good example is FAULHABER's BXT flat motor family, capable of enabling high torque in very small packages with integrated encoder solutions, it offers the precise control surgeons require. Gear ratios and feedback systems are often also customised to allow surgical robots to hold steady positions or respond quickly to subtle movements.

Neurosurgery is a field where even greater precision is required. Brushless motors with integral gearing and high-resolution encoders provide the stable accurate control the applications require, offering smooth motion without overshoot.

One of the most significant aspects is haptic feedback. High-end micromotors that offer smooth, responsive torque can transfer realistic tactile feel to surgeons so that they can feel the pressure being applied on delicate tissues. Further ahead, advances in AI and robotics could lead to autonomous performing systems with the capability to perform some functions independently; this would enable operations to be faster, safer and more effective.

At the heart of each successful robot is a motor tailored specifically to meet the requirements of its intended use. From performance and power to size and reliability, the right motor specification lays the groundwork for performance and longevity. Having suppliers on board from the beginning who you can rely upon, ensures motors are appropriately designed and purchased from day one, without delays and redesign costs. With the UK pushing to catch up in the robotics race, getting motor selection has never been more important.

Dave Walsha is sales and marketing director at Electro Mechanical Systems (EMS)

www.ems-limited.co.uk