Bio-inspired approach for adaptive monitoring and fault-tolerant control of electro-hydraulic actuators

The human body has evolved to work with specific blood flow and blood pressure through various feedback mechanisms allowing for adaptations to maintain blood flow and pressure at adequate levels. For example, in cases of acute bleeding, blood pressure decreases due to blood volume loss. Then. Reflex tachycardia signals, as a physiological response in the form of a feedback mechanism, signals the brain to increase heart rate, compensating for a drop in blood pressure. Taking inspiration from such biological feedback mechanisms, we proposed a reconfigurable fault-tolerant control and monitoring framework for electro-hydraulic systems to address performance degradation problems such as leakage faults causing a pressure drop. The framework incorporates two concurrent feedback mechanisms designed to maintain system performance and stability under faulty conditions. More specifically, we develop an adaptive monitoring algorithm (a higher-order sliding mode observer) that allows for the estimation and reconstruction of the leakage faults that cause a pressure drop and consequently performance degradation in the systems. The second set of adaptive feedback mechanisms leverages the signals generated by the monitoring algorithms to adjust and regulate the system's supply pressure and the control algorithm. These adaptive feedback-control algorithms enable the system to continue operating normally despite the presence of leakage faults.

A bio-inspired approach for increased efficiency of servo actuators through a switching control configuration

Nature is the most impressive source of inspiration for engineers making more capable systems. Across nature, the movement of some animals strongly depends on their environment, which means passive locomotion. In this type of mobility, the environment- air or water -is a propulsion because its direction is essentially the same as the animal movement. For instance, jellyfish and flatworms just swim along the flow. The blue crab and continental-shelf fish such as plaice can sense the direction of a tidal flow whether it is favorably directed or not, to use it for increasing their speed of swimming. Hydraulic actuators are usually in interaction with their environment to exert torques and forces. Sometimes, the direction of the external load exerted by the environment is the same as the actuator’s desired movement. The main objective of this research is to exploit the external load of the environment as a propulsion in motion tracking. In this condition, the hydraulic system finds a secondary supply of energy that leads to increased efficiency. To this aim, a new arrangement of control valves is used to have a controllable supply pressure and regulate the system pressure according to the actuator's demands. In an encounter with assistive loads, the system pressure decreases and the external load is used to move in the desired direction. The H-infinity control strategy is used to synthesize suitable control algorithms for motion tracking in the presence of model uncertainties.