To improve the control performance of the permanent magnet synchronous motor speed control system, the fractional order calculus theory is combined with the sliding mode control to design the fractional order integral sliding mode sliding mode surface (FOISM) to improve the robustness of the system. Secondly, considering the existence of chattering phenomenon in sliding mode control, a new second-order sliding mode reaching law (NSOSMRL) is designed to improve the control accuracy of the system. Finally, the effectiveness of the proposed strategy is demonstrated by simulation.

A new threshold circuit technique is proposed for a vibration sensing circuit that operates at a nanowatt power level. The sensing circuits that use sample-and-hold require a clock signal, and they consume power to generate a signal. In the use of a Schmitt trigger circuit that does not use a clock signal, a sink current flows when thresholding the analog signal output. The requirements for millimeter-sized wireless sensor nodes are an average power on the order of a nanowatt and a signal transition time of less than 1 ms. To meet these requirements, our circuit limits the sink current with a nanoampere-level current source. The chattering caused by current limiting is suppressed by feeding back the change in output voltage to the limiting current. The increase in the signal transition time that is caused by current limiting is reduced by accelerating the discharge of the load capacitance. For a test chip fabricated in the 0.35-µm CMOS process, the proposed threshold circuits operate without chattering and the average powers are 0.7-3 nW. The signal transition times are estimated in a circuit simulation to be 65-97 µs. The proposed circuit has 1/150th the power-delay product with no time interval of the sensing operation under the condition that the time interval is 1s. These results indicate that, the proposed threshold circuits are suitable for vibration sensing in millimeter-sized wireless sensor nodes.