Biomedical Signal Processing and Control 40 (2018) 10–22 Contents lists available at ScienceDirect Biomedical Signal Processing and Control jo ur nal homep age: www.elsevier.com/locate/bspc Research Paper Analysis of surface electromyography signal features on osteomyoplastic transtibial amputees for pattern recognition control architectures Talon Garikayi a,∗ , Dawie Van den Heever a , Stephen Matope b a Biomedical Engineering Research Group, Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, South Africa b Department of Industrial Engineering, University of Stellenbosch, South Africa a r t i c l e i n f o Article history: Received 21 January 2017 Received in revised form 29 June 2017 Accepted 5 September 2017 Keywords: Myoelectric control SENIAM Electromyography Pattern recognition Prosthetic Amputee a b s t r a c t This paper presents the characterisation of electromyography signals for the purpose of controlling a powered prosthetic ankle using pattern recognition algorithms. The goal is to identify the specific muscles that can be used to guarantee optimal control of a multichannel powered prosthetic ankle. SENIAM and ISEK protocols were used for signal acquisition, processing and reporting. A set of paired surface electrodes were placed above selected muscles on the residual limb. Participants were instructed to perform normal gait. The signals were recorded, labelled and analysed using the Vicon Nexus Motion Capturing System and Noraxon Myomotion System. Signal processing was performed using MR3 Software and further post processing was performed using Matlab. Time and frequency domain features were analysed. The protocol revealed that the tibialis anterior, medial and lateral gastrocnemius muscles actively generate myoelectric signals on the residual limb. A total of 12 time domain and 4 frequency domain features were successfully extracted and used in the analysis. The tibialis anterior muscle was identified as a candidate for classifying dorsiflexion with a mean amplitude of 35.08 V. The soleus muscle was inaccessible on the amputated leg and as a result only the medial and lateralis gastrocnemius muscles, with 17.40% signal power and 43.73% mean amplitude as compared to the soleus, were available for plantarflexion. There was significant difference (p < 0.05) between features from the amputated residual limb and those from the intact normal leg. However, there was no significant difference (p > 0.05) between signal features from two different participants. Sagittal plane movements were linearly discriminated with 100% accuracy for tibialis anterior and medial gastrocnemius. However, lateralis gastrocnemius exhibited a 0.0769% classification error as a result of the amputation technique. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Electromyography (EMG) is a process which involves detection, analysis and use of electromyography signals [1]. These signals have found application in both clinical diagnosis, assistive technology and engineering [2]. In this study the focus is on assistive technol- ogy. Lower limb amputees have struggled for long to acquire neural intuitive powered ankle devices so as to aid mobility [3]. As a result this has reduced the confidence the amputees have on the pros- thetic limbs. The ankle dorsiflexion and plantarflexion movements are responsible for the proper toe-off and heel-off during normal gait. The propulsive force generated by the ankle enable smooth ∗ Corresponding author. E-mail addresses: talon@sun.ac.za, talongarikayi@gmail.com (T. Garikayi), dawie@sun.ac.za (D. Van den Heever), smatope@sun.ac.za (S. Matope). forward body projection and minimises hip rotation. The natural ankle intuitively adapt to desired gait thereby assisting the body to achieve full range of motion for all anatomical angles such as the hip and the knee. The ankle facilitates the attainment of smooth normal gait, however, the use of stiff mechanical prosthetic ankles presents some difficulties for amputees which may lead to abnor- malities within the gait [4]. The poor range of motion and lack of intuitive control of the ankle may result in short term effects such as bruises and long term effects such as lower back-pain. Therefore there is a need for more a naturally controlled ankle prosthesis and this can be achieved with the use of electromyo- graphy signals. Such a technique will present the amputees with intuitive control of the ankle thereby achieving close to natural gait. However, challenges exist on selecting the proper muscles to use and also the poor quality of the electromyography signal available at the amputated limb present challenges on signal processing. http://dx.doi.org/10.1016/j.bspc.2017.09.007 1746-8094/© 2017 Elsevier Ltd. All rights reserved.