Modular designs in lightweight robots are gaining popularity for their flexibility in handling specialized tasks. As part of building a robot in-house, optimizing the drive train that powers and controls each joint is critical to its performance. The most effective approach is to develop the drive train as a complete module, according to Roman Berger, maxon’s head of business development for robotics.
The rise of modular robots and the significance of drive train design
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As robots increasingly require specialization for specific tasks, the benefits of modular robots come into play. Their ability to alter form and configuration using modular components, unlike fixed-body robots, provides enhanced flexibility. This allows for frequent and rapid reconfiguration or customization of a modular robot. Additionally, should the robot malfunction, replacements can be quickly and economically sourced.
There is a notable shift towards modular designs in the sector of lightweight robots and collaborative robots (cobots). These smaller units, typically handling loads from 3kg to 16kg, are well-suited for specialization and the advantages of modularity. Their compact size facilitates easier configuration, and there is a high demand for these robots across various tasks, as evidenced by the annual growth rates of 20% to 40% in the deployment of lightweight robots globally.
To support the demand for modular robots, there is also a growing need for more flexible robot control. Motion controller manufacturers and PLC manufacturers are now providing kinematic libraries that simplify robot control programming. This enables system integrators and end-users—from automotive manufacturers to logistics and delivery services—to develop their own robots, reducing dependence on traditional robot manufacturers. The benefit is improved robotic control tailored more specifically to their needs, with the ability to swiftly adapt to changes.
Motor Design
Central to the trend towards modular, lightweight robots is the need to power their kinematic motion. The motion system, or drive train, is responsible for moving and controlling each robotic joint. Just as the modular robot design must allow for versatility in performing specialized tasks, the drive train must also be capable of meeting these demands.
The motor is a crucial part of the drive train. To achieve high dynamic performance, essential attributes include high torque density and low inertia, which enable rapid acceleration and deceleration. Smooth control of each robot joint is also crucial, so the motor needs to support features such as low cogging to minimize micro ripples and jerks during rotation.
For lightweight robots, a compact motor design is essential, which further underscores the need for high torque density. A frameless design, like maxon’s EC frameless motor, facilitates design integration, and its hollow shaft allows for the routing of cables through it. Despite its small size, this motor design also meets critical requirements for heat and energy efficiency.
The Drive Train
However, to optimize robot motion performance, it is not enough to consider just the motor; the entire drive train must be taken into account. The drive train, a module in itself, typically includes the motor, gearhead, encoder (which continually provides feedback on position and speed), and the motors’ position and speed controller. Like the motor, each component must be designed to meet specific performance criteria, and designing the drive train as a complete module is key to optimizing motion performance.
This involves proper dimensioning and sizing to meet required motion output values such as torque, speed, acceleration, and position profile. Often, the specialized requirements of modular robots for each application also mean that customization of individual motion components is necessary.
Since these components work together, changes to one part can affect the entire motion system’s operation. Thus, treating the drive train as a complete module is a more effective way to optimize both motion performance and design integration.
To achieve these objectives, the design process should also include kinematic simulation. Creating a working, virtual model is crucial for planning the robot’s motion path and ensuring that the desired kinematic profiles are achieved, according to factors such as position, acceleration, and torque. Simulation is also essential to ensure that the robot operates within safe limits for the protection of users and the physical environment. This service can be provided by a motion designer like maxon, along with programming support for each axis of motion.
Optimizing Design Efficiency
Designing and simulating the drive train as a module also makes the development process significantly more efficient. Most importantly, it eliminates the time needed to develop and test the performance, compatibility, and integration of individual drive system components. It also reduces the workload on procurement teams. As a result, robots can be brought online more quickly.
While the alternative approach of procuring distinct components may seem attractive from an initial cost perspective, the time required for in-house drive train engineering can make this process less cost-effective in the long run.
The greatest advantage of engaging with dedicated motion engineering expertise is the enhanced motion performance that can be achieved. Not only does this partnership increase a robot’s capabilities, but a tried and tested approach to drive train development also enhances reliability, minimizing downtime
