AN AUTONOMOUS CONTROL AND MONITORING SYSTEM FOR A LOWER LIMB ORTHOSIS : THE GAIT PROJECT CASE J. C. Moreno, F. J. Brunetti, J.L. Pons Instituto de Autom´ atica Industrial, CSIC (Spain) ABSTRACT A wearable control and monitoring system has been devel- oped for a novel active orthotic device. The development covers the need of an autonomous tool for gait analysis dur- ing normal use of the orthotic device. The system has two basic components: the Base Unit and the Ambulatory Unit. The units communicate by means of a Bluetooth link. In order to test the system, a knee-ankle-foot orthosis has been instrumented for gait control and monitoring of biomechan- ical and comfort data during daily use by patients with mus- cular deficiencies. This paper describes the system devel- oped, outlines its performance and presents measurements recorded while performing different activities. 1. INTRODUCTION Lower leg disorders affecting human mobility have been commonly treated by means of orthoses to partially com- pensate functional loss. These devices are used to modify structural or functional characteristics of the neuromuscu- loskeletal system. Knee-Ankle-Orthoses (KAFOs) are pre- scribed for subjects with orthopedic and neurological dis- eases mainly to provide stability to the joint when muscles are weak. Commercially available KAFOs guaranty secu- rity while keeping joints locked but result in non-cosmetic and high energy demanding patterns. Other systems adapt more dynamically during gait, controlling the knee joint during the swing phase triggering a mechanism based on ankle range of motion (Utx Swing Orthosis) or managing the loading response by springs (Becker). This evolution sets the basis for research efforts in enhancing autonomy. Autonomy of a system for use by a disabled is a cru- cial goal in mobility restoration by artificial means; portable technologies have been proposed to assist human impaired motor control [1]. Gait control strategies to recover or im- prove mobility with KAFOs can be classified with regard to the type of control actions on joints, segments or muscles: The work presented in this paper has been carried out with the finan- cial support from the Commission of the European Union, IST programme under contract no. IST-2001-37751, ”GAIT – Intelligent Knee and An- kle Orthosis for biomechanical evaluation and functional compensation of joint disorders” locking/releasing, braking, damping or powering. Most ex- plored technique to control gait, functional electrical stimu- lation (FES) has been reviewed [2]. Hybrid systems, com- bining FES with orthoses to provide ambulation to para- plegic patients have been explored widely [3]. Discomfort related to stimulation is the major problem of this technique and results are not evidence of a good control of body mo- tion neither energy expenditure reduction. Engineering at- tempts on adaptation of brakes [4] and clutches [5] to knee braces have been reported. Actuators designed for robotic systems, have been proposed to correct drop foot [6] con- trolled by external computers. Systems for autonomous use have been designed on the basis of microcontroller and mi- croprocessor technologies for automatic correction of gait, mostly for application of implantable stimulation. Regard- ing sensors for gait control, foot switches have been used initially for synchronization of stimulation signals [7]. Prob- lems associated with the switches reliability have guided to approaches considering other sensors as goniometers, tilt sensors, and accelerometers [8] have been proposed for de- tection of events to control FES. The gait monitoring systems give clinician useful in- formation to calibrate and optimize prescription of rehabli- tation equipment. This tool would also help therapists in training patients in the use of new orthotic devices. Com- monly, calibration of KAFOs is trail and error procedure based on clinician experience. Electronic for orthotic devices were developed [9], [4], [10] but all of these works were oriented to control. There also exists gait monitoring devices like step counters. The purpose of this device is to help to measure physical activity under free-living conditions. By now there are no system that measure gait biomechanical parameters under normal life. Moreover, a lack of information about performance dur- ing daily activities with orthoses is latent. Biomechanical and clinical evaluation has been always developed in the laboratory context. Activity Monitoring during daily use of an autonomous KAFO would redound in the improve- ment of the prescription and rehabilitation processes while providing useful information to the involved specialists. For all the above, we propose in this paper a novel au-