A throttle-less single-rod hydraulic cylinder positioning system: Design and experimental evaluation

Abstract

Modern industrial tote dumpers and lifters are equipped with long-stroke single-rod hydraulic cylinders. For years, valvecontrolled cylinders have been used in tote dumpers. Valve-controlled actuators are highly inefficient due to huge power losses in throttling valves. They also need a cooling system to remove the wasted heat energy from the hydraulic oil. This article introduces a low-cost throttle-less hydraulic circuit to control the single-rod cylinder of a tote dumper. The system consists of a motor-driven gear pump, an On/Off solenoid valve, to redirect the differential flow of the single-rod hydraulic cylinder and a counterbalance valve, which makes the circuit controllable for assisting loads and keeps the load in position with no effort from the hydraulic pump. Experimental results demonstrate the performance of the circuit. A test rig has been designed to simulate a lifting load. The energy efficiency of the circuit is determined by comparing a valve-controlled circuit with the proposed circuit. The proposed circuit composition is not only efficient and simple but is also accurate in terms of position response using a proportional controller. The circuit is easy to control since the only needed measurement is the displacement of the actuator. The circuit, however, does not recycle energy.

Design, Implementation and Evaluation of a Pump-Controlled Circuit for Single Rod Actuators

“…In other regions, motion is controlled in a throttle-less manner. Throttling of hydraulic fluid creates a pressure drop across the valve orifices maintaining increased pressure in cylinder chambers compared to pump ports, which contribute towards a stiffer actuator [21,25]. The proposed circuit possesses a comparable energy efficiency and energy regeneration ability to the circuit with POCVs at high loading conditions and the stability of the circuits with throttling valves at low loading conditions.…”

“…Generally, CBVs are throttling valves used for safety requirements through the whole working range actuator operation. They have been used in some pump-controlled applications [6,15,21,26], but with no ability to regenerate energy [21]. Here, the CBVs are utilized to only restrict flow at low loading conditions to enhance the performance while allowing free flow at high loading conditions to allow energy regeneration.…”

“…The differences between p 1 and p A and p 2 and p B are due to the losses in the transmission lines. This pressure drop is calculated using the lumped resistance model as follows [21]:…”

“…Both designs are more energy efficient as compared to conventional valve-controlled alternatives and accurate enough for many industrial applications. Nevertheless, these designs cannot regenerate energy [21]. From the above discussion it is seen that in spite of the large amount of studies on the topic, throttle-less actuation technology for single rod cylinders has not been fully explored, compared to valve-controlled actuation, in terms of dynamic performance [22].…”

“…Jalayeri et al [6,21] and Altare and Vacca [15] introduced the idea of regulating the load motion with the help of counterbalance valves, which belong to throttling elements. To compensate for the differential flow Jalayeri et al [21] used an on/off solenoid valve and a check valve, while Altare and Vacca [15] utilized a special form of shuttle valve, which they called a dual-pressure valve. Both designs are more energy efficient as compared to conventional valve-controlled alternatives and accurate enough for many industrial applications.…”