چكيده به لاتين
Intraspinal microstimulation (ISMS) is a promising technique to reactivate the movement in hindlimbs through electrical stimulation of the lumbosacral portion of the spinal cord below the lesion. One major issue in the control of the movement using ISMS is the development of control strategy to generate the electrical stimulation patterns. The problem of motor control using intraspinal microstimulation (ISMS) can be approached at two levels of the motor system: individual muscles (motor pools) and movement blocks (module). The major challenges of direct ISMS at the level of individual muscle are the number of electrodes that are required to be implanted in order to recruit all muscles involving the motion and the muscle selectivity. One solution to cope with these problems is the control of movement generated by appropriate combination of the movement primitives. The main goal of this project is the designing of adaptive fuzzy terminal sliding mode controller (AFTSMC) for control of the walking on the moving treadmill using a new stimulation strategy based on the movement blocks (synergistic flexion and extension of the ankle, knee and hip joints) through ISMS. By adapting the pulse width of the stimulation signals and appropriate combination of the movement blocks, the accurate tracking performance in air-stepping and walking control were achieved.
The movement control results from spinally-intact adult cats of either sex (domestic short hair, 2.5–4.5 kg body weight) were reported in this project. The mean of the results over 16 cats showed that using two movement blocks, the ankle, knee, and hip joints were controlled seperately, with the tracking error 9.6% (normalized root mean square (NRMS)), 11.7% and 14.0%, respectively. According to this result, the four blocks were selected for the closed-loop control of air-stepping. The averages of tracking error, over five cats, were 9.3%, 11.2%, and 16.1%, for the ankle, knee, and hip joints, respectively. During treadmill-walking control, the measured knee and ankle angles were fed back for closed-loop control of the two blocks. The averages of NRMS error over three cats are 14.9%, 16.0%, and 18.2% for the ankle, knee, and hip joints, respectively, for the right leg and 17.4%, 19.0%, and 26.5% for the left leg. The results of the current study demonstrated that the normal gait pattern can be achieved by tracking control of the movement blocks using ISMS, while the controller requires no offline learning phase and no pre-adjustment of thestimulation level. The controller is able to automatically regulate the interaction between the movement blocks withoutany preprogrammed block activities. One major challenge in controlling the stepping is the time delays found in the control input and in the response of the neuromusculoskeletal system. Moreover, in this project, a new fast AFTSMC was designed for uncertain nonlinear systems in the presence of external disturbances subject to simultaneous known, time-varying state and input delays.
