No abstract

The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal.

No abstract

No abstract

A lattice-matched In0.53Al0.22Ga0.25As/InP heterojunction bipolar transistor has been fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). No potential spike due to zero conduction band discontinuity at the emitter-base heterojunction is obtained. Meanwhile, the larger valence discontinuity (ΔEV=460 meV) than AlGaAs/GaAs and InGaAs/InP systems provides this structure with a better hole confinement. An offset voltage as low as 50 mV along with a current gain of 85 is achieved.