Using feedback linearization to alter the performance of multiple linear hydraulic-actuators powered by the same pump
[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In this study, a feedback linearization technique is presented to improve the tracking and energy performances of a hydraulic system using multiple linear hydraulic-actuators with both actuators being powered by the same pump. This research uses two open-centered 4-way valves to control the displacement of the two hydraulic actuators for a wheel loader implement system, based upon an input command from the operator who is modeled as a first-order system with a bandwidth frequency of 2 Hz. The feedback linearization control method is used to adjust the operator input based on the measurement of fluid pressure on one side of each actuator, and the pump pressure that supplies both valves with no additional sensing needed. The feedback linearization improves the tracking performance as measured by the R-squared value and increases the bandwidth frequency for lift and dump actuator thereby the operator's fatigue is decreased by 7.50, 7.25, and 6.75 times for the lift actuator and 6, 4, 4.5 times for the dump actuator under constant, step, and sinusoidal loading, respectively. Also, the feedback linearization reduces the overall energy consumption for the system during an applied step load by 9.79 [percent] , however, it increases the consumption by 0.37 [percent] and 5.12 [percent] during applied constant and sinusoidal loading, respectively. Moreover, a slight increment in feedback linearization gains reduces the energy consumption by 8.82 [percent], 18.52 [percent], and 4.75 [percent] during an applied constant, step, and sinusoidal loading, respectively. Finally, the feedback linearization technique improves the robustness of the system by rejecting external disturbances and nearly eliminating the load dependence of the tracking response over a wide range of operating frequencies. This finding suggests that the operators should have less difficulty learning how to operate the machine with this controller, and the overall productivity of the machine should increase.