Một số sử dụng hệ thống kiểm soát thông tin phản hồi trong đó chuyển động theo chu kỳ chung là được theo dõi trong giai đoạn swing và lập trường của các bước, và kích thích liên tục được điều chế bằng cách sử dụng tỷ lệ / tách rời / phái sinh (PID) kiểm soát (Veltink, 1991), | Tapping into the Spinal Cord for Restoring Function after Spinal Cord Injury 19-5 employ the use of manual push-buttons built into walkers and crutches to initiate the swing phase of each step. Some systems use feedback control in which cyclic joint movements are tracked during the swing and stance phases of the stepping and stimulation is continuously modulated using proportional integral derivative PID control Veltink 1991 or neural networks Abbas and Triolo 1997 . State control of stepping has also been deployed in systems that use artificial learning to determine an appropriate set of sensor signals to generate appropriately timed transitions between the swing and stance phases Andrews et al. 1988 Popovic et al. 2003 . Alternatively fuzzy logic is used to determine gait events during stepping Skelly and Chizeck 2001 . An evaluation of control strategies for restoring stepping using FES was conducted by Popovic et al. 2003 . Their results indicate that automatic control of ballistic walking has a lower metabolic cost than either automatic control of slow walking or pushbutton activated control. However the volunteers preferred the latter forms due to the ability to coordinate upper and lower limb movements. These findings demonstrate the importance of developing an appropriate control scheme to be used in conjunction with FES systems. Intraspinal Microstimulation Intraspinal microstimulation is a technique that uses fine microwires to apply stimulation within the ventral horn of the spinal cord below the level of the injury to generate functional movements of the legs. The ISMS microwires are implanted in a compact and relatively motion-free region of the cord and thus minimal strain is experienced by the implant during evoked limb movements. The target region for implantation is the lumbosacral enlargement which is approximately 5 cm long in humans and contains all the motoneuron pools that innervate the muscles of the lower extremities as well as large .
