Control of posture with FES systems

Abstract

One of the major obstacles in restoration of functional FES supported standing in paraplegia is the lack of knowledge of a suitable control strategy. The main issue is how to integrate the purposeful actions of the non-paralysed upper body when interacting with the environment while standing, and the actions of the artificial FES control system supporting the paralyzed lower extremities. In this paper we provide a review of our approach to solving this question, which focuses on three inter-related areas: investigations of the basic mechanisms of functional postural responses in neurologically intact subjects; re-training of the residual sensory-motor activities of the upper body in paralyzed individuals; and development of closed-loop FES control systems for support of the paralyzed joints.

Controlling balance during quiet standing: Proportional and derivative controller generates preceding motor command to body sway position observed in experiments

“…In literature, it has been suggested that a PD controller can theoretically stabilize an inverted pendulum of human body size when the system's closed-loop time delay is not too long [16]. In an extreme case where the closed-loop time delay is zero, the PD controller acts as a regulator of mechanical stiffness and viscosity [16].…”

“…In an extreme case where the closed-loop time delay is zero, the PD controller acts as a regulator of mechanical stiffness and viscosity [16]. It has also been pointed out that a long closed-loop time delay in the neural control system can destabilize the intrinsically unstable human bipedal stance: Morasso and Schieppati [2] applied a PD controller to regulate the balance of an inverted pendulum in simulations and discovered that a closed-loop time delay of about 50 ms was sufficient to destabilize the system.…”

Sagittal spinal alignment in paraplegics: a new paradigm for the rehabilitation under neuromuscular electrical stimulation

“…Although obtaining postural control and balance in paraplegics has been attempted through NMES, Matjacic et al 10 observed that the strategy is effective only when it incorporates the voluntary and reflex actions of the neurologically intact upper body. For them, the balance in paraplegics in a standing position can be obtained through the 'strategy of the hips' in a double-inverted pendulum.…”

“…New systems are being developed to eliminate two problems associated with NMES: muscle fatigue and non-functional bipedal posture due to the need for a hand support to maintain the posture and to achieve balance. 10 Aiming at allowing an interaction with the environment, Matjacic and Bajd 2 proposed a strategy to control the bipedal posture in paraplegics with hands free. Their theory model was based on a mathematical model of an interconnected double-inverted pendulum that ignores the mobility and shape of the spine and begins to accept the entire body segment above the hips as a single rigid structure.…”

Genetic Algorithms Based Approach for Designing Spring Brake Orthosis – Part Ii: Control of FES Induced Movement

“…So far classical closed-loop control algorithms have failed to provide satisfactory performance and have not been able to guarantee stability, a desired property of the controlled system [27]. Jaime et al [26] and Matjacic et al [30] implemented PID controllers for unsupported standing in paraplegic subjects. Hunt and co-workers used Hinfinity control [22,24] and linear quadratic Gaussian control [16] for unsupported standing in paraplegic subjects.…”