Existing robotic lower-limb prostheses use autonomous control to address cyclic, locomotive tasks, but are inadequate in adapting to variations in non-cyclic and unpredictable tasks. This study aims to address this challenge by designing a novel electromyography (EMG)-driven musculoskeletal model for volitional control of a robotic ankle-foot prosthesis. The proposed controller ensures continuous control of the device, allowing users to freely manipulate the prosthesis behavior. A Hill-type muscle model was implemented to model a dorsiflexor and a plantarflexor to function around a virtual ankle joint. The model parameters for a subject specific model was determined by fitting the model to the experimental data collected from an able-bodied subject. EMG signals recorded from antagonist muscle pairs were used to activate the virtual muscle models. This model-based approach was then validated via offline simulations and real-time prosthesis control. Additionally, the feasibility of the proposed prosthesis control on assisting the user's functional tasks was demonstrated. The present control may further improve the function of robotic prosthesis for supporting versatile activities in individuals with lower-limb amputations.

Diesel generators are an integral component of remote islanded microgrids in rural Alaska. As inverter-based generation is integrated in these microgrids, adequate transient modeling will be necessary as dynamic and transient stability issues can arise with significant contributions of inverter-based generation. A complete transient model of a diesel generator includes models of the machine, exciter, governor, and any relays or other limiting components. Few studies compare the adequacy of various types of diesel generator governor or exciter models or include a volts/hertz (V/Hz) limiting functionality commonly found in diesel generators deployed in such remote islanded microgrids. This paper introduces and compares diesel generator models in response to two load steps against responses from the ACEP PSI lab 400 kVA diesel generator which represents a realistic diesel generator found in remote islanded Alaskan microgrids. A simplified governor model is introduced and compared to the traditional DEGOV governor model, and the functionality of a V/Hz limiter added to a DC4B exciter is demonstrated.

Ankle joints play key roles in everyday locomotion, such as walking, stair climbing, and sit-to-stand. Despite the achievement in designing powered prosthetic ankles, engineers still face challenges to duplicate the full mechanics of ankle joints, including high torque, large range of motion (ROM), low profile, backdrivability, and efficiency, using electric motors and related transmissions. In this study, our goal was to develop a new active prosthetic ankle, Variable Spring embedded Motor-ball screw (VSeM) ankle, to meet all these requirements at the same time. Using a manually adjustable elastic element, which is parallel with our motor actuator, we can readjust the ROM of VSeM to handle all normal locomotion tasks. VSeM’s capability to mimic human ankle was validated through both bench tests and human subject tests.

This paper presents seamless transiton between the grid-connected and islanded mode of microgrid. The prominenece of the seamless transition is to maintain the load voltage and frequency as well as constant power delivery during both the modes of operation of microgrid. In this paper voltage source converter (VSC) of PV generating unit operates in PQ control mode in both grid-tied and islanded operation of microgrid due to its intermittent characteristics. While VSC of battery storage system (BSS) operates in PQ control mode during grid-tied operation and in VF control mode during islanded operation of microgrid. A fuzzy logic controller has been designed for VF control during the islanded mode of operation of microgrid. The fuzzy logic controller can efficiently deal with non linearity of power system as it does not depend on the mathematical model of the system. Also the proposed fuzzy logic controller limits the switching transients as well as voltage swell and sags during the fault. The simulation results proves the optimal working of proposed control strategy in achieving the seamless transitions between the grid connected and the islanded modes of operation of microgrid.