To turn a motion concept for a robotics application into reality, dedicated engineering expertise can be invaluable.
Antonio Herrera
Global Strategic Marketing – Surgical and Industrial Robotics
Portescap
Robotics is among the fastest growing technologies today, transforming a multitude of segments in consumer, industrial and commercial applications. The increasing use of robotics is enhancing efficiency, safety, and productivity in the manufacturing sector including industrial automation applications. Beyond industrial applications, robots are also enhancing lives in medical settings, such as improving precision in surgery, which can improve the patient outcome and speed up recovery.
This diversity in applications means that, dependent on the robot’s purpose, OEMs have an array of considerations to make in their designs. Central to all robots, whatever the application, is the motion control technology – motors, gears, and feedback devices, that drives the limbs, joints, and end effectors. The application requirements of the robot have significant implications on the design of the motion system.
Not only does motion design require an assessment of the technology that can solve the challenge most efficiently, but it must also satisfy commercial needs for the OEM. This means the motion system must optimally integrate with the overall robot design, while ensuring ease of assembly and regulatory compliance.
Calculating the working points is a primary step for engineers when designing electromechanical systems such as those in robotic applications. Determining torque, radial and axial loads are critical factors in the motion system design. Alongside these fundamental needs, the kinematic demands of a robot are vital. This includes the motion profile of the device, and how smooth, responsive, and precise this movement should be – all factors that depend on the performance of the motion control system.
Increasingly, for some applications, a crucial element to the dynamic performance of a robot is miniaturization. A compact, lightweight system has low inertia that enables responsiveness, and low mass also optimizes efficiency. Moreover, a micro motion system is essential because of demands on the overall design footprint. To suit the characteristics of many robots and the environments in which they operate, these motion systems must fit within limited physical space – and integrate smoothly with other components. In fact, more and more robotic systems being designed and built today feature an increased level of component integration as well as close coupling among components. This leads to reductions in losses and power usage, and increases system efficiency and ultimately performance. Yet in achieving this, the motion system must still meet the required operating points and desired motion profile.
In addition to these needs, reliability is also paramount. Maintenance challenges or a failure in an industrial automation setting can mean downtime, but in a medical setting reliability can impact human safety. Miniaturization of the motion system adds complexity considering the demands of thermal management, and engineers must also take into account component compatibility, working points including overload and continuous operation, along with other potential failure modes. The operating environment is also important for reliability, which includes considering temperature and the potential for ingress, so the motion system’s design must ensure adequate protection.
From concept to manufacture
Only after investing time and effort for research into these design considerations, and a concept has been developed, can a design be created. Yet the progression from the conceptual design of a motion system to one that can be achieved on a manufacturing scale is significant. The need to revise or change technical attributes and previously selected components, or even materials selection, can introduce roadblocks that add significant time to project development.
Prioritizing motion system design requirements at the earliest stage helps to reduce the challenge of moving from prototype to full production. This ranges from the fundamental level of balancing torque output with thermal management and footprint requirements, to long-term reliability considerations involving choice of motor technology and material selection.
This balancing act can be less burdensome with the support of an experienced partner who is well versed in addressing these challenges. Moreover, a motion expert can point towards critical factors, previously unconsidered, that could impact the delivery of the project at a later timescale – potentially reducing significant time and cost that could otherwise be added in rework.
By relying on motion control experts that offer diverse, application-specific solutions, combined with an understanding of manufacturability methods and awareness of commercial challenges, robot developers can achieve the optimum path for motion development. This can also involve the choice between commercial-off-the-shelf (COTS) solutions and customization. What’s more, a significant benefit of working with a dedicated motion expert is the technical support available throughout the entire development process to ensure maximum reliability and integration.
Focus on motors
Robotic applications use a diverse range of motor types, depending on application requirements. For instance, miniature brush dc, brushless dc, and stepper motors can be found in the most challenging robotic applications, including collaborative robots, grippers, service robots, prosthetics, exoskeletons, and rehabilitation devices all the way to life critical tools such as surgical robots. And specific application requirements can dictate the type of motor used. For example, in some cases, frameless motors are a good choice for applications that are space-limited or must strictly control inertial mass. And newer applications such as SCARA robots and their end effectors need torque with low mass in the smallest possible footprint.
Sometimes, helping a customer involves not a custom design but specifying the best motor fit for the application. For example, Portescap recently specified a motion solution for an existing humanoid robot design. The robot manufacturer needed compatibility with their existing drives and controls but wanted to increase torque density and reduce mass. This would be central to improving the robot’s precision by optimizing control of movement, increasing responsiveness, and reducing inertia.
The robot developer also wanted to extend battery lifetime, so the motors needed to have high efficiency. With more than 20 motors per unit, and robots used across a diverse array of environments, reliability was also a priority. The relatively high number of motors per robot, combined with the purchasing demands of the end- user markets, meant that the need to balance cost with value was also important.
The engineering team determined that the characteristics of a brushed dc motor would best fulfil the requirements. Providing simplicity of control, this motor design would ensure integration with the humanoid’s existing architecture. While achieving the cost-point required by the OEM, the inherent characteristics of a brushed dc motor would be well-matched to a humanoid’s close human interaction, where the advantages of high torque at low speed would enable fine control.
Taking into account the array of options in robotic motion development, it’s essential to think beyond the parameters of speed and torque. Not only will the motion system directly impact the robot’s performance, but it will have strong implications for its long-term reliability.
Turning the optimum concept into a manufactured reality is also where expertise can be essential. By partnering with a dedicated motion engineering team, a viable commercial solution, developed to a much closer timescale, is more likely to be achieved. Ideally, this relationship between robot OEM and motion developer should start as early as possible in the project to optimize the outcome.
Portescap
www.portescap.com
Filed Under: Industrial automation, Robotics • robotic grippers • end effectors, Motion Control Tips
