Bio-Inspired Conceptual Mechanical Design and Control of a New Human Upper Limb Exoskeleton

Safe operation, energy efficiency, versatility and kinematic compatibility are the most important aspects in the design of rehabilitation exoskeletons. This paper focuses on the conceptual bio-inspired mechanical design and equilibrium point control (EP) of a new human upper limb exoskeleton. Considering the upper limb as a multi-muscle redundant system, a similar over-actuated but cable-driven mechatronic system is developed to imitate upper limb motor functions. Additional torque adjusting systems at the joints allow users to lift light weights necessary for activities of daily living (ADL) without increasing electric motor powers of the device. A theoretical model of the “ideal” artificial muscle exoskeleton is also developed using Hill’s natural muscle model. Optimal design parameters of the exoskeleton are defined using the differential evolution (DE) method as a technique of a multi-objective optimization. The proposed cable-driven exoskeleton was then fabricated and tested on a healthy subject. Results showed that the proposed system fulfils the desired aim properly, so that it can be utilized in the design of rehabilitation robots. Further studies may include a spatial mechanism design, which is especially important for the shoulder rehabilitation, and development of reinforcement learning control algorithms to provide more efficient rehabilitation treatment.

Optimal control of pulse compensators of oscillatory phenomena in a network oil and gas pipeline system

Within the framework of oil and gas engineering, the problem of optimal control of pulse compensators that counteract harmful oscillatory phenomena in a continuous medium during transportation via network gas-hydraulic carriers is considered. Powerful compressor units that create high pressure in the carrier of a continuous medium, to a large extent contribute to the formation of undesirable oscillatory phenomena (pulsations) that occur at the output of these compressors. These ripples are transmitted to the network carrier environment, which significantly reduces the efficiency of compressor units and even causes accidents in the networks of gas and hydraulic carriers. The latter means that the software engineering of the oil and gas industry should include research in the direction of improving the reliability of operation of compressor units and gas-hydraulic carriers. In the presented study, the mathematical description of the oscillatory process of a continuous medium is carried out by formalisms of a differential-difference system of hyperbolic equations with distributed parameters on a graph. At the same time, the mathematical model contains a fairly accurate mathematical description of controlled pulse compensators. The problem of controlling pulse compensators of an oscillatory process is considered as the problem of a point control action on a controlled differential-difference system at the places where continuous medium vibration dampers are connected to a network carrier. This is a characteristic feature of the presented study, which is quite often used in practice when engineering the processes of transporting various kinds of continuous media through network oil and gas carriers. The study essentially uses the conjugate state and the conjugate system for a differential-difference system - the relations determining the optimal point control are obtained. The results of the work are applicable in the framework of oil and gas engineering to the study of issues of stabilization and parametric optimization.

Adaptive parameter optimal energy management strategy based on multi-objective optimization for range extended electric vehicle

With the aim of economy improvement, emission reduction and prolonging the battery service life, an adaptive parameter optimal energy management strategy is proposed for range extended electric vehicle and a method of multi-objective optimization (MOO) is proposed. Firstly, two strategies based on different threshold parameter types, namely velocity-switch-based multi-operation-point control strategy (MCS v–b) and power-switch-based multi-operation-point control strategy (MCS p–b) are designed. Then, the oil-electric conversion loss rate, comprehensive exhaust emission, and battery capacity loss rate are selected as the optimization objectives. The barebones multi-objective particle swarm optimization is applied in MCS v–b and MCS p–b for solving the MOO problem. The simulation results show a clear conflict that three optimization objectives cannot be optimal under the same solution. And then, the individual with optimal comprehensive objective is taken as the final optimization solution to evaluate the performance of the proposed methodology. As expected, the proposed MCS p–b has a positive effect on prolonging the battery service life while ensuring high fuel economy and low emission. Experimental test results thoroughly validate the proposed approach and this result can be used to improve comprehensive performance levels.

An Effective Self-Powered Piezoelectric Sensor for Monitoring Basketball Skills

Self-powered piezoelectric sensor can achieve real-time and harmless monitoring of motion processes without external power supply, which can be attached on body skin or joints to detect human motion and powered by mechanical energy. Here, a sensor for monitoring emergent motion is developed using the PVDF as active material and piezoelectric output as sensing signal. The multi-point control function enables the sensor to monitor the sequence of force order, angle change, and motion frequency of the “elbow lift, arm extension, and wrist compression” during shooting basketball. In addition, the sensor shows can simultaneously charge the capacitor to provide more power for intelligence, typically Bluetooth transmission. The sensor shows good performance in other field, such as rehabilitation monitoring and speech input systems. Therefore, the emerging application of flexible sensors have huge long-term prospects in sport big data collection and Internet of Things (IoT).

Perbandingan Performa Refrigeran Propana dan Amonia pada Siklus Refrigerasi Dew Point Control Unit (DPCU)

Natural gas, that has been processed and met certain specifications, is sent to consumers through pipeline. Gas condensation within the pipeline should be avoided because it has negative impacts. Hydrocarbon dew point is a measure of the easiness of gas condensation. To meet the hydrocarbon dew point, heavy hydrocarbon should be extracted in dew point control unit (DPCU). The extraction is done by gas cooling in gas chiller followed by separating the liquid formed in low temperature separator (LTS). The gas chiller functions as an evaporator in the DPCU refrigeration cycle. Propane is a common refrigerant in the DPCU. In addition, ammonia is also a potential refrigerant due to its normal boiling point being close to the hydrocarbon dew point. Refrigeration cycle performance depends on evaporator temperature, condensor temperature, and the inherent pressure-enthalpy (PH) characteristic of the selected refrigerant. This study aimed to compare the performance from ammonia and propane against the change of evaporator and condenser temperature. This study was a dry research using Aspen Hysys V11.0 simulation software (academic license). The refrigeration cycle was a simple cycle with fixed variables in the form of evaporator load, saturated liquid at outlet condenser, and saturated vapour at outlet evaporator. This study indicated that at the same evaporator load, evaporator temperature, and condenser temperature, ammonia refrigeration cycle was better than the propane because coefficient of performance (COP) of ammonia was higher than propane. This study also modeled COP changes of propane and ammonia as mathematical equation. Quantitatively, it appeared that COP of propane was more sensitive than ammonia against both evaporator and condenser temperature changes.Keywords: ammonia; condenser; evaporator; propane; refrigeration cycle; simulationA B S T R A KGas alam yang telah diolah dan sesuai spesifikasinya dikirim ke konsumen melalui pipa. Kondensasi gas dalam pipa harus dihindari karena menimbulkan dampak negatif. Titik embun hidrokarbon menjadi ukuran kemudahan proses kondensasi gas. Untuk mencapai titik embun hidrokarbon yang diinginkan, maka hidrokarbon berat harus diekstraksi di dew point control unit (DPCU). Ekstraksi dilakukan dengan cara mendinginkan gas di gas chiller lalu memisahkan cairan yang terbentuk di low temperature separator (LTS). Gas chiller tersebut berfungsi sebagai evaporator pada siklus refrigerasi DPCU. Propana adalah refrigeran yang umum digunakan di DPCU. Selain itu, amonia juga menjadi refrigeran yang potensial karena kedekatan titik didih normalnya terhadap titik embun hidrokarbon yang diinginkan. Performa siklus refrigerasi dipengaruhi oleh temperatur evaporator, temperatur kondensor, dan karakteristik tekanan-entalpi (PH) yang melekat pada refrigeran yang dipilih. Penelitian ini bertujuan untuk membandingkan performa siklus refrigerasi propana dan amonia terhadap perubahan temperatur evaporator dan kondensor. Penelitian ini merupakan penelitian kering yang menggunakan perangkat lunak simulasi Aspen Hysys V11.0 (lisensi akademik). Siklus refrigerasi yang digunakan adalah simple cycle dengan variabel tetap berupa beban evaporator, kondisi cair jenuh outlet kondensor, dan kondisi uap jenuh outlet evaporator. Hasil penelitian ini menunjukkan bahwa pada beban evaporator, temperatur evaporator, dan temperatur kondensor yang sama, maka siklus refrigerasi amonia lebih baik dari propana karena COP amonia lebih tinggi dari propana. Penelitian ini juga memodelkan nilai COP propana dan amonia sebagai persamaan matematika. Secara kuantitatif, terlihat bahwa COP amonia lebih stabil dari propana terhadap perubahan temperatur evaporator dan kondensor.Kata kunci: amonia; evaporator; kondensor; propana; siklus refrigerasi; simulasi