A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump

Electro hydrostatic activators support for the electrification of heavy duty systems. To achieve less energy consumption, our method concentrates on optimization, electro variable displacement pump utilization of the systems. Our modeling, and the simulation method supports the preliminary design.

Our electro variable displacement pump, which should choose complete performance prediction, automatic parameter generation, and design robustness. Begin by classifying the parameters to design the electro variable displacement pump or EVDP. Assign the independent parameters, representing each component to the active category, and the parameters derived from the active parameters to the driven category.

Then designate the parameters calculated, using empirical functions to the empirical category. To develop the estimation models, estimate the pump and motor driven parameters from the active parameters, using the scaling laws. Use the component catalogs to estimate the driven parameters for the gearbox and the ball screw from the active parameters.

Assess the pump, the gearbox, and the ball screw efficiencies by empirical functions, and estimate the thermal resistances for the thermal network model developed with the empirical functions from the thermodynamics theory. Build the weight model of the EVDP in MATLAB by adding up the weights of each component and then conducting the dynamic lumped parameter modeling of the EVDP in the system simulation platform. Next conduct thermal modeling of the EVDP in the system simulation platform by setting a thermal network for the EVDP.

For lifetime and reliability modeling, use the fatigue life of the ball and the wear life of the piston pump unit as its lifetime. Model the ball screw and piston pump unit lifetime with the equations. Assume the reliability of the ball screw and the pump corresponding to its lifetime, is 0.90, and define the reliability as calculated at the 50, 000th working hour.

Then model the ball screw and piston pump unit reliability with the equation. Proceed to assemble the model by placing all the equations of each node together to form the model block for each node. Then conclude the input and output variables of each node.

Define the inputs and outputs of the overall EVDP model and perform the causality analysis of all the nodes. When necessary add additional nodes to ensure that all the nodes are causally linked. Then connect all the nodes to form the overall model of the EVDP.

Once the EVDP model is formed, verify the modeling method using the EVDP prototype and test rig. To do so, install the EVDP on a test rig, consisting of a loading part and a control part. Then connect the three EVDP ports to the hydraulic circuit of the loading part, and the EVDP electric cables to the control part.

Conduct the prototype testing by pushing the start button on the panel and starting the auxiliary hydraulic power. After deactivating the mode valve with the button on the panel, set the sweeping frequency displacement command to the EVDP in the text box of the user interface. Record the EVDP displacement response, and derive its magnitude and phase characteristics.

To analyze the experimental results set the active parameters of the EVDP prototype to the model built earlier. The model will generate other required simulation parameters automatically. Set the environment temperature, and initial EVDP temperature at 40 degrees Celsius, and run the simulation model under the same conditions as the EVDP prototype test to record the simulation results.

To check the model accuracy, plot the experimental and simulation results of each condition group in one figure. To perform the simulation analysis of the EVDP design, set the dynamic and thermal models by clicking on the parameter mode tab and selecting the TFFD31 option. Then go to the file name for simple fluid characteristic data tab to import the oil property file.

Under the parameter mode use the THGCV01 or THGCV02 blocks. To set the environment temperature as described in the manuscript input the active parameters to the parameter estimation models. Then click on the run button under editor tab to run the script for generating all the simulation parameters.

In MATLAB, use the run button under editor tab to run the script for calculating the weight and activating the dynamic and thermal models with the simulation parameters. The simulation results will be obtained by the script automatically. With the run button under editor tab, run the script for calculating the EVDP lifetime and reliability performance from the saved simulation results.

Go to the simulation mode in the system simulation platform to check the results. Then derive other EVDP performance results from these time domain simulation results. To set the simulation parameters, check the parameter mode.

Then use the run button under editor tab to run the script for activating the dynamic and thermal models. Later, press the simulation mode tab to check the sensitivity and uncertainty analyses. The temperature dynamics of different EDVP parts are shown here.

The representative analysis illustrates the EVDP efficiency under a full duty cycle. Under the full load condition, the EVDP achieved a total efficiency of around 80%Later, the absolute losses of the EVDP dropped, along with the efficiency decrease. The sweeping frequency response examined the EVDP dynamic performance.

In the projected performance of the EVDP, a good control accuracy with a 0.09 degree error was predicted, whereas pump lifetime and reliability was found to be the weakest. After building the proposed models, the complete preliminary design method can be developed. The method can enhance the applicability of the electro variable displacement pump, and the associated electro hydrostatic activators.

This method resolved common challenges of design stage, such as parameters certainty, and multidisciplinary simulations. This leads to more reliable, preliminary design of the pump for electro hydrostatic activators.