The biomechatronics wrist prosthesis uses ultrasonic sensors as the input, servo motors as the output, and a microcontroller. Photograph courtesy of study authors Nasrul Anuar Abd Razak, Noor Azuan Abu Osman, Hossein Gholizadeh, and Sadeeq Ali.
A team of researchers from the Department of Biomedical Engineering, University of Malaya, Kuala Lumpur, Malaysia have developed and tested a new prosthetic system, known as a biomechatronics wrist prosthesis, for individuals with transradial amputations. The results of the preliminary study were published April 23 in the open access journal BioMedical Engineering OnLine.
The transradial prosthetic system was developed by replacing the Bowden tension cable of a body-powered prosthesis with two ultrasonic sensors, two servo motors, and a microcontroller placed inside the prosthetic hand. The ultrasonic sensors are placed on the shoulder to transfer left-to-right and up-and-down motion detected from the head to the microprocessor and microcontroller-based system to generate the wrist movement of the prosthesis. One servo generates the pronation/supination movement while the second servo generates flexion/extension movement. The servo motor has a similar degree of rotation as a biological wrist, and is able to generate greater torque than that required to perform daily tasks. The power supply comes from nine-volt batteries.
The kinematics of the wrist movement-pronation/supination and flexion/extension-were tested using motion analysis and compared to the general motion of the human hand. The study also evaluated the required degree of detection for the input of the ultrasonic sensor to generate the wrist movements. Motion analysis testing showed that the biomechatronics prosthetic system was reliable for the completion of common tasks in daily life. The degree of rotation and degree of supination between a biological hand/wrist and the biomechatronics wrist prosthesis were similar. The head needed to bend about 45 to 55 degrees of rotation or about 14 to 16cm to provide the full input wave to the sensor.
The researchers said that while their biomechatronics system is not a replacement for the current body-powered system, replacing the tension cable with an ultrasonic sensor may lead to future advancements for this device.
