Liberating Technologies Introduces Advanced Prosthetic Arms

The Boston Digital Arm, developed by Liberating Technologies, utilizes one of the most advanced signal-processing technologies to provide far more flexible prosthetic arms for transhumeral (above the elbow) amputees than analog and microprocessor-based control systems. Transhumeral amputees will now be empowered with the kind of flexibility and strength from a prosthetic far beyond what they could achieve from their older devices.

Developed by using TI’s Code Composer Studio Integrated Development Environment (IDE), this assistive technology product is controlled by signals generated from one or more of a user’s undamaged upper limb muscles. The myoelectric signals generated during muscle contractions are detected, amplified and are compared in strength to signals from other sensors to determine how much voltage is to be sent to motors in the elbow, wrist and hand.

Boston Digital Arm’s control system has superior capabilities such as accepting almost any myoelectric signal as input and controlling more motors than any other prosthetic system. This assistive technology product’s programmability allows it to electrically lock with the Liberating Technologies’ shoulder joint and act as a drive option. This kind of motion facility makes it possible for users to move their arms at the shoulders, which was not possible earlier.

The myoelectric signals are captured by tiny sensors placed on the surface of the user’s skin. Digital filtering by the digital signal processor (DSP) ensures that the signals are do not suffer interference from external noise. The prosthesis has a selectable notch filter that operates at 60 Hz for use in US and 50 Hz for use in Europe.

This assistive technology offers the advantage of natural movement, meaning that the user does not have to stop and think about what muscles to flex to make a particular motion. In fact, a user has the ability to operate more than one motor at a time, permitting simultaneous control, which enables the user to reach out and open the hand to grasp something in a single, smooth motion.

DSP-based processing power facilitates accessibility to lifting power as well as control of the operating speed so that when the motor reaches a predefined power limit, its speed is reduced to save battery and to prevent it from getting overheated.  

Bill Hanson, president of Liberating Technologies said, “This approach offers the potential to provide every artificial limb user with an arm that has been customized to suit their capabilities and personal preferences.”  

Currently, Liberating Technologies engineers have incorporated 28 control strategies for various arm movements. They are regularly devising new strategies to meet unique user requirements.

Source: LTI Boston Arm Systems