Simulation and experimental evaluation of a combustion-powered actuator for hopping

Abstract

A combustion-powered actuator has been proposed in our previous work (Wang et al., 2015), and it has shown great power hopping ability. To explore the hopping process and output performance of the actuator, the model of an actuator driving the hopping process is investigated through theoretical analysis and experimental validation. Firstly, the structure of the actuator and hopping process are described briefly, and the dynamic models of the process are constructed. Secondly, the thermodynamic model of the actuator is established by the Wiebe heat release function and the input energy density is computed by Chemkin for when propane and nitrous oxide with different equivalence ratios are injected into the chamber. Thus, the thermodynamic model is obtained by integrating dynamic and thermodynamic equations. After that, a few output performance parameters are identified to assess system performance. Lastly, the experimental rig of the combustion actuator is set up to test the displacement and pressure of the actuator driven hopping process. By solving the thermodynamic equations, the post-combustion pressure, the displacement and the velocity varying with time are computed, and are compared with the test results, indicating that the computational results match the experimental test well. At the end of the stroke, the velocities of the experiment and simulation are 6.5 m/s and 6.99 m/s, respectively. The hopping results are compared with the simulation when different pressures under equivalence ratio of 1 are injected, and the maximum and minimum deviations are 14.45% and 1.83%, respectively.