Electro-Hydraulic Drive of the Variable Ratio Lifting Device under Active Load

Hydraulic systems fed by fixed displacement pumps driven by frequency-controlled electric motors can replace conventional throttling systems due to their ability to control the speed of hydraulic cylinders regardless of the value and direction of the load. These systems can improve the energy efficiency of the drive or even provide the possibility of energy recuperation during lowering. This paper presents experimental studies of the new drive system with volumetric control of the speed of the lifted/lowered payload using the example of a scissor lift. The system uses a reversible gear pump driven by an asynchronous motor fed by a frequency inverter operating in field-oriented control mode. Comparative studies of the mapping of the assumed speed of the hydraulic cylinder and platform are presented, as well as studies of the influence of the load change on the speed and positioning of the mechanism driven by the open-loop controlled system.

Energy model of transport machines with braking energy recovery

Most of the time, modern transport vehicles operate in unsteady modes. Undoubtedly, the reasons for the decrease in the efficiency of machines are fluctuations in speed and load, their deviations from the optimal values cause an increase in energy losses. Another reason for the increase in energy losses is the process of forced braking when it is necessary to stop the car. A class of vehicles with hybrid propulsion systems that can recover braking energy are currently being developed. Significant advantages among them are transport vehicles with a flywheel energy storage, which have a long service life. This article discusses the energy model of transport vehicles with the possibility of braking energy recuperation.

A Novel Design Concept of Digital Hydraulic Drive for Knee Exoskeleton

Hydraulic actuation of exoskeletons has gained interest among researchers due the potentials of high power density and energy recuperation allowing the reduction of mass and space used by the device (when compared to the traditional electrically actuated exoskeletons). However, developing a light and cost-effective design of such exoskeleton remains a key challenge. In this work, a novel design of digitally driven knee exoskeleton is presented. The design uses simple hydraulic cylinders instead of multi-chamber cylinders (which are typically used in digital actuations and are expensive). The design also includes a unique mechanism that is able to satisfy the peak torque requirements during a typical gait cycle with a smaller hydraulic force. This ensures small size of hydraulic components and a moderate power demand from the energy source. To study this exoskeleton design, a numerical model of the exoskeleton and the lower limb is developed in this work. The simulation results show that the design is able to track the motion of the knee in a typical gait cycle as well as satisfy the necessary torque requirements.

Magnetic circuit optimization of linear dynamic actuators

<p class="Abstract">Contactless braking methods (with capability of energy recuperation) are more and more widely used and they replace the traditional abrasive and dissipative braking techniques. In case of rotating motion, the method is trivial and often used nowadays. But when the movement is linear and fast alternating, there are only a few possibilities to break the movement. The basic goal of research project is to develop a linear braking method based on the magnetic principle, which enables the efficient and highly controllable braking of alternating movements. Frequency of the alternating movement can be in wide range, aim of the research to develop contactless braking method for vibrating movement for as higher as possible frequency. The research includes examination and further development of possible magnetic implementations and existing methods, so that an efficient construction suitable for the effective linear movement control can be created. The first problem to be solved is design a well-constructed magnetic circuit with high air gap induction, which provides effective and good dynamic parameters for the braking devices. The present paper summarizes the magnetostatics design of “voice-coil linear actuator” type actuators and the effects of structure-related flux scattering and its compensation.</p>

Innovative solution of hybrid hydraulic fire wood splitting machine

Hybrid powertrains have already proven themselves as viable solutions for reducing fuel consumption while maintaining the same operating performance of conventional ones, which is achieved by using an additional energy source in combination with energy recuperation. Many forestry machinery and tools which are intended for field use are hydraulics-based and powered by tractors or skidders. These tools may also be hybridized by incorporating a properly-sized hydraulic accumulator. This paper proposes an innovative solution of hydraulic fire wood splitting machine which uses a hydraulic accumulator in order to increase its efficiency. A simple model of conventional and hybridized machine is developed and presented in this paper. The model is then simulated over a defined operating cycle with realistic loads. Simulation results show that hybrid structure may improve the splitting performance with lower power requirements. Finally, the conventional and hybridized machine performances are compared and discussed.

Comparing the physical principles of action of suspension damping devices based on their influence on the mobility of wheeled vehicles

This paper reports the comparison of two physical principles of action of suspension damping devices based on their influence on the mobility indicators for an 8×8 wheeled machine. A radical difference between these principles of action is the dependence of resistance forces on the speed of the relative movement of working bodies (internal friction: hydraulic shock absorbers) or on the relative movement of working bodies (external friction: friction shock absorbers). Widespread hydraulic shock absorbers have certain disadvantages that do not make it possible to further increase the mobility of wheeled or tracked vehicles without the use of control and recuperation systems. In turn, in friction shock absorbers, the use of new materials has eliminated many of their shortcomings and thus can provide significant advantages. It was established that the application of friction shock absorbers for a given wheeled vehicle did not significantly affect the speed compared to hydraulic ones. The main factor that prevented the implementation of the advantages of friction shock absorbers was the insufficient suspension travel. However, friction shock absorbers absorbed 1.76...2.3 times less power, which reduced the load on nodes and increased efficiency (autonomy). In addition, a more uniform load on suspensions was ensured, which improved their resource, and, due to the prevailing vertical oscillations of the suspended body over the longitudinal-angular ones, the geometric passability improved as well. The comparison of two physical principles of action of damper suspension devices in a wheeled vehicle has shown that the use of friction shock absorbers could provide significant advantages in resolving the task relates to improving the mobility and would fundamentally affect the choice of the suspension energy recuperation system if it is applied.

A regenerative braking energy recuperation from elevator operation in building by active rectifier

Elevators- means of vertical transportation to carry people and goods are an indispensable part in offices, high-rise buildings, hospitals, commercial areas, hotels, car-parks when blooming urbanization develops worldwide. However, the level of energy consumption in elevator operation is significant, so energy saving solutions have been outlined and applied in practice. With frequent braking phases, regenerative braking energy is wasted on braking resistors. Therefore, this paper proposes regenerative braking energy recuperation method for elevator operation in building by active rectifiers enabling the braking energy to be fed back into utility grid. Simulation results conducted by MATLAB with data collected from OCT5B building-RESCO new urban area, Ha noi, Vietnam have verified saving energy of using active rectifiers replacing diode rectifiers up to 33%.