Regaining Mobility through Bionic Limbs and Power-Dense Motion Solutions

The loss of mobility can be devastating, but the ability to move can potentially be regained and independence re-established through the use of bionic limbs. Also referred to as myoelectric prostheses or microprocessor prostheses, bionic limbs are artificial limbs that work by utilizing signals from a person’s muscles to move. These can be controlled either by a myoelectrical signal, using impulses of the residual limb to control the prosthesis, or a microprocessor, through sensors to collect position and accelerating data and an algorithm to determine proper motion.

How Bionic Limbs Utilize Motion Solutions

In the case of motor-driven, battery-powered bionic limbs, miniature motion solutions power the rotation at the joint to drive the limb movement. They are well-suited for both upper limb systems, including the shoulder, elbow wrist, hand, and lower limb systems, such as the hips, knees, ankles, and feet. The larger motion system, which prioritizes power density and high efficiency in a compact envelope, is usually a mix-and-match of components, such as a motor and gearhead or motor, gearhead, and encoder.

Small brush DC motors are typically utilized for enabling finger joint movement, while flat brushless DC motors are used for larger joint movement. Bionic arms often utilize DC motors because they are simple to drive without electronics, while bionic knees employ flat brushless DC motors because they have more room for additional electronics, as well as feature a higher power density and efficiency. Motion accessories like gearheads and encoders are also ideal for this application. Gearheads are employed to increase torque and fine-tune the motion system, and encoders provide precise feedback that is correlated to the joint position, such as the exact precision level of a knee or finger opening and closing.

Motion Solution Considerations for Bionic Limbs

Due to the sensitive nature of these devices, here are five parameters to consider when creating the ideal motion solution:

• Small Size/Lightweight. End users require these devices to be as natural and unobtrusive as possible, so the newer product generations are becoming increasingly smaller and lightweight.
• Power Density. Although the devices are being reduced in size, they must retain the ability to close the fingers quickly and with high grip strength (i.e. holding on tightly to an object or supporting the weight of the person using the device). A power-dense motor accomplishes just that.
• High Efficiency. Bionic limbs are battery-powered devices, so a high-efficiency motion control system is necessary to limit frequent and inconvenient recharging.
• Precision Control. Because these limbs are replicating natural limbs, they must move smoothly, naturally, and predictably – similar to how a natural limb is expected to move.
• Speed/Torque Balance. The motion control system must blend together a delicate balance of speed and torque parameters to naturally flex the joint.

Looking for a miniature motor supplier for your bionic limb application? Our engineering expertise and customization capabilities position Portescap as an ideal partner to deliver power-dense and efficient solutions. Explore our motors for prosthetic limbs or reach out to us directly to discuss your applications!