Abstract-This paper presents a generic formal model for the specification and design of the sequential control for lower-limbs training machines. An object extension of Statecharts is used as a modeling formalism. The resulting hybrid and hierarchical control system interprets the required training specifications for a particular user to execute the corresponding sequence of switching (position, speed and force) control laws. Keywords -Training and rehabilitation machines, hierarchical control, Statecharts, object design, Switching Control laws. I. INTRODUCTIONTraining and rehabilitation machine for the lower limbs are becoming widely used today [1]. The design and the development of the control system for such machines is faced with a number of scientific and technical challenges. The domain-specific knowledge should therefore be exploited to provide assistance for this design and development process, by proposing a generic reusable model that can easily be specialised for the development of the control system for any particular training machine.The main goal of the control system of a lower-limbs training machine is to execute a co-ordinated training sequence, alternating an upward movement and a downward movement. The type of the movement (velocity, position, and/or force controlled) is to be determined as a function of the required training mode for a particular user. The control system is also required to handle other tasks such as: initialisation, calibration of the effort measurement to take the gravity force into account, management of user's safety, as well as other specific features.The aim of this paper is to propose a hierarchical formal model that capture the generic sequential control requirements related to the co-ordination and the execution of the identified movements and tasks. Section 2 presents the requirement analysis of the sequential control and coordination system and introduces an object extension of Statecharts, which is next used in Section 3 to specify the required generic sequential control model. II. REQUIREMENT ANALYSIS AND SPECIFICATION FORMALISMTraining machines should be able to carry out different training configurations to comply with the diversity of requirements in medicine and sports. A preliminary analysis of different training configurations [2], [3] has shown that a training phase, in general, is characterised in terms of the muscular group, the training mode, the training type, and the movement direction involved (Table 1). These terms define the direction of the muscular force, the required movement type for a specific training or rehabilitation phase, the nature of the required muscular force, and the movement direction, respectively. Table 1 also shows that three control laws (position, velocity, and force) are required to carry out the different movement types. This analysis also shows that a sequential controller for a training machine should be structured into three levels (Fig. 1). A training session comprises a number of successive phases. A phase corresponds t...
Abstract-This paper presents the control system of a machine for training and rehabilitation of lower limbs. This system is based on the execution of a sequence of switching (position, speed and force) control laws corresponding to the required training configuration. Some illustrative training results are also discussed. Keywords-Rehabilitation machine, training machine, fuzzy logic control, switching control laws, weight machine. I. INTRODUCTIONMulti-Iso (Fig. 1) is a computer-controlled machine for training and rehabilitation of the lower limbs. This machine, which is destined for medicine and sports, is the result of a joint project involving the Laboratoire d'Automatique et de Microélectronique (Reims-France) and the company Myosoft (Bellegarde-France). Multi-Iso is based on original concepts that provide significant improvements over existing machines, including precise rehabilitation adapted to user needs, and dedicated training possibilities to improve physical performance and autonomy. The architecture of Multi-Iso (Fig. 2) comprises a software and control part, a mechanical part, and an electronic part. The functioning principle consists in applying a torque delivered by a brushless motor to one (or both) lower limb(s). This motoring action allows the user to attain a nominal force of 200 deca Newtons (daN) at the ends of the limbs and a speed of 400°/sec under maximum load. Six other motors, not shown in Fig. 2, are also used to position the seat, either manually or automatically to a memorized position, so as to suit the needs and the morphology of the current user [1].Multi-Iso can carry out different training configurations whose importance in medicine and sports are discussed in [1]. Seven training modes (Isokinetic, Steering, Isometric, Isotonic, Physiokinetic, Stretching, and Assisted) are implemented, and some of them are original and were developed specifically for Multi-Iso [2]. The specific training sessions, defined by a physiotherapist with the help of a domain-specific man-machine interface, are translated into a corresponding switching sequence of force, position or speed control laws that perform the required movement patterns. Training results are stored in a database to be subsequently processed. The control system comprises a PC-based supervisory module that handles the organization and the coordination of the activities involved in the training sessions, and a micro-controller-based module implementing the switching control laws.This paper presents the control system of Multi-Iso; the synthesis of the switching control laws will be particularly emphasised. Some training results are given to illustrate the efficiency of the control system, despite the simplicity of the implemented control laws. II. CONTROL SYSTEM OF MULTI-ISOThe control system of Multi-Iso (Fig. 3) belongs to the class of switching systems, which is a sub-class of hybrid dynamical systems. The established medical specifications CONTROL LAW IMPLEMENTATION FOR MULTI-ISO: A TRAINING MACHINE FOR LOWER LIMBS Abstract ...
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