An Overview of Exoskeleton Devices, Their Performances, and Limitations

Advancements in sensor technology have driven significant progress in biomedical fields, particularly in the development of exoskeletons. Currently, four types of exoskeleton devices exist: powered, passive, pseudo-passive, and hybrid. Powered exoskeletons rely on electric cables or batteries to function, essentially acting as artificial muscles for the user. Passive exoskeletons provide support without the need for an electric system, focusing on mechanical assistance. Pseudo-passive systems incorporate some electric components but primarily serve a supportive function rather than enhancing muscle power. Hybrid systems combine the features of powered exoskeletons, using electronic components triggered by sensor readings from the user’s muscles or nerves.

Many powered exoskeletons, such as the device from Rex Bionics, are bulky and battery-powered. While they offer benefits like adjustability for all users and ease of use, they suffer from limited battery life (about one hour) and bulkiness, making prolonged rehabilitation exercises difficult for patients. Cyberdyne's HAL is a hybrid device that detects bioelectric signals to facilitate movement and incorporates an interface to control user movement intentions. However, as a battery-powered system, it shares the same drawback of limited battery life, restricting long-term mobility.

In addition to technical limitations, affordability remains a significant barrier. For example, the DYNSYS X1 Exoskeleton is lightweight, features a relatively long battery life, and uses artificial intelligence to match the user’s gait in real-time. However, its price—around $1,300—remains a considerable expense. The average exoskeleton typically ranges from $5,000 to $50,000, making them financially inaccessible for most patients.

To address these limitations, the Assistive Bionic Joint (ABJ) was developed at San Jose State University. This hybrid exoskeleton utilizes a combination of electromyography (EMG) sensors, inertial measurement unit (IMU) sensors, and rotary encoders to capture the user’s motion and trigger the device’s fluidic muscles to match the user’s gait in real-time. The ABJ is designed to be lighter and more cost-effective than many existing alternatives, representing a promising advancement in assistive technology. This poster will present the overall performance of the ABJ, highlighting the significance of the various sensors incorporated into the device and their impact on its operation.