Fluid Power & Machine Intelligence Lab.

A novel generation of Independent Metering hydraulic circuit is proposed. Three electro-hydraulic poppet valve (EHPV) valves and one typical directional control valve are used in this configuration to reduce the system cost and energy consumption. This configuration has the potential to overcome the control difficulties of the typical four-valve circuits while it provides the same number of metering modes. Moreover, the regenerative flow does not connect directly to the high-pressure flow from the pump so, it is possible to save more energy by flow regeneration. The control equations for each metering mode are developed in such a way that these can be expressed as a simple orifice equation based on equivalent valve conductance and equivalent pressure concepts. Therefore, this configuration guarantees the energy-saving and operate smoothly.

This work focused on developing the new generations of power sources which normally included Proton Exchange Membrane Fuel Cell – Batteries – Supercapacitor. The digital twin models were developed to mimic the real power sources using the Internet of Things (IoT). The fault diagnosis and remaining useful life were designed to predict the status and lifetime of each device. The energy management strategies were proposed based on online and offline optimization methods to make sure that the power sources could work in optimal working conditions. A real test bench was successfully fabricated and the results showed that the lifetime of devices was extended, minimized the hydrogen consumption, and maintain the SOC of supercapacitor and battery in ideal ranges.

Hydraulic systems are widely applied in many fields due to the high-power-to-weight ratio and large force/torque output compared to pneumatic or electrical actuation systems. Hence, the research of hydraulic system, especially hydraulic manipulator is deeply researched in our Lab. This research field include 3 sub-topics as position tracking control, fault-tolerant control and force control for hydraulic manipulator. 1) In the position tracking control topic, the target is how to guarantee high-accuracy tracking performance in joint space or Cartesian space of the hydraulic manipulator suffering from the model uncertainty, uncertain parameters, external disturbance and highly-nonlinearity of the actuator dynamics. 2) In the fault-relating topic, the problem is divided into fault diagnosis, which includes fault detection, fault isolation and fault identification with various types of faults as sensor faults (e.g., position, pressure) and actuator fault (e.g., internal leakage), and fault-tolerant control algorithm which utilizes the information from fault diagnosis block to reconfigure the control structure and compensate for the effect of faults on the control system. 3) In the force control topics, there are two problems as indirect force control (i.e., impedance control) which requires the system to mimic a virtual compliance behavior (e.g., spring-mass-damper) to avoid high contact force and dangerous interaction with human, and the direct force control which is designed to guarantee high-accuracy force tracking performance of the control system during operation.

This research topic mainly focuses on the triboelectric energy harvesting strategies and their applications based on the fluid-based triboelectric nanogenerator (Flu-TENG), such as by proposing a new direct charge transfer in a streaming flow, which is called Direct charge Transfer - TriboElectric NanoGenerator(DT-TENG). Besides, we developed a discontinuous-conduction-based rotary triboelectric nanogenerator based on liquid-solid electrification. By using the motion-activated switch structure, the induced charges can accumulate on one electrode and then release to another electrode at a specifically designated position. Taking advantage of this process, we can maximize the charge transfer per cycle which also improves the output performance of the developed TENG. Moreover, the output performances of TENGs rely highly on the efficiencies of the processes for triboelectric charge generation and for separating positive and negative charges. Thus, the surface charge density can be enhanced by injecting ions concentration. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is very useful as a material to fabricate polymer membranes. Ionic liquids could be added to form a supercapacitor system that involves conveying the electrical double layer (EDL) characteristics and the negative charge in the electrification layer. To the end, a new Flu-TENG by using the triboelectric layer consisting of PVDF-HFP and ionic liquid (IL), namely PIL membrane, has been proposed. In currently, a self-powered pulsating flow sensor has been proposed by using the water-PVDF surface contact electrification. And the magnetic field is investigated its effect on the fluid, it is analyzed how the negative and positive ions motion or concentrate in the dielectric layer and free ions.

The control scheme is designed to satisfy three performance requirements of the active suspension system: 1) Ride comfort: Adaptive backstepping control is proposed to stabilize the chassis and dissipate the external disturbances that cause continuous excitations to the passengers. 2) Road holding: The tire is always kept in contact with the road surface by remaining the relative tire fore (RTF) should not exceed one. RTF is used to evaluate the driving safety factor and can be described by comparing the dynamic tire force with the total weight of the frame, wheel, and tire. 3) Handling stability: The suspension space must be within the limited range of structural design.

This topic builds the bilateral haptic teleoperation system (BHTS) driven by pneumatic artificial muscle (PAM) actuators applying studied control approaches. The BHTS enables human users to conduct remote complex tasks in spatial decoupling or inaccessible environments, while can be able to provide the haptic perception of being present for the human operator. The strategy of this study begins with developing independent control for each feature of the master and slave system. We study methods to solve several problems in the teleoperation such as high accuracy tracking performance without chattering phenomena, time delay issue, a friction-free disturbance factors, but a bare minimum requirement is to guarantee the system stability. In additional methods, a series of adaptive force observers are researched to external forces without using any force. Especially, to increase the responsiveness to an unknown environment and human behavior, several advanced studies in turn for slave-environment interaction and human-mater collaboration task are based on the learning mechanism, for example, a model-free control or optimal control based on reinforcement learning.