Blair Lock

Publications (3)3.46 Total impact

• Article: Use of two-axis joystick for control of externally powered shoulder disarticulation prostheses.

  Robert D Lipschutz, Blair Lock, Jonathon Sensinger, Aimee E Schultz, Todd A Kuiken
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  ABSTRACT: We explored a new method for simple and accurate control of shoulder movement for externally powered shoulder disarticulation prostheses with a two-axis joystick. We tested 10 subjects with intact shoulders and arms to determine the average amount of shoulder motion and force available to control an electronic input device. We then applied this information to two different input strategies to examine their effectiveness: (1) a traditional rocker potentiometer and a pair of force-sensing resistors and (2) a two-axis joystick. Three nondisabled subjects and two subjects with shoulder disarticulation amputations attempted to control an experimental externally powered shoulder using both control strategies. Two powered arms were tested, one with powered flexion/extension and humeral rotation and one with powered flexion/extension and adduction/abduction. Overwhelmingly, the subjects preferred the joystick control, because it was more intuitively linked with their shoulder movement. Additionally, two motions (one in each axis) could be controlled simultaneously. This pilot study provides valuable insight into an effective means of controlling high-level, externally powered prostheses with a two-axis joystick.
  The Journal of Rehabilitation Research and Development 01/2011; 48(6):661-7. · 1.78 Impact Factor
• Article: Real time ECG artifact removal for myoelectric prosthesis control.

  Ping Zhou, Blair Lock, Todd A Kuiken
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  ABSTRACT: The electrocardiogram (ECG) artifact is a major noise source contaminating the electromyogram (EMG) of torso muscles. This study investigates removal of ECG artifacts in real time for myoelectric prosthesis control, a clinical application that demands speed and efficiency. Three methods with simple and fast implementation were investigated. Removal of ECG artifacts by digital high-pass filtering was implemented. The effects of the cutoff frequency and filter order of high-pass filtering on the resulting EMG signal were quantified. An alternative adaptive spike-clipping approach was also developed to dynamically detect and suppress the ECG artifacts in the signal. Finally, the two methods were combined. Experimental surface EMG recordings with different ECG/EMG ratios were used as testing signals to evaluate the proposed methods. As a key parameter for clinical myoelectric prosthesis control, the average rectified amplitude of the signal was used as the performance indicator to quantitatively analyze the EMG content distortion and the ECG artifact suppression imposed by the two methods. Aiming at clinical application, the optimal parameter assignment for each method was determined on the basis of the performance using the suite of testing signals with various ECG/EMG ratios.
  Physiological Measurement 04/2007; 28(4):397-413. · 1.68 Impact Factor
• Article: CAPTURING SHOULDER MOTION AS AN INPUT FOR EXTERNALLY-POWERED, SHOULDER DISARTICULATION PROSTHESES

  Robert D Lipschutz, Jonathan Sensinger, Blair Lock, Todd A Kuiken
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  ABSTRACT: Prosthetists have been fitting externally-powered components to individuals with “shoulder disarticulation”, upper extremity amputations for decades. These components have ranged from momentary contact switches that permitted carbon-dioxide to pass through tubes in order to create an articulating motion, to force sensitive resistors (FSRs) that vary the amount of resistance between thin conductive plates in order to permit varied current to flow and provide input to an electrical motor. Activation of these types of inputs requires contact by the user with their remaining residual limb or, in the case of individuals with congenital deficiencies, phocomelic digits. A variety of pull switches have also been used to harness the body motions provided by the user, which activate an electro-mechanical switch used to drive a motor. With the use of coupled rotary potentiometers, the authors have chosen to investigate a unique approach to ipsilateral shoulder motion as a control source for two degrees of freedom.