Search results for "hydraulic cylinder"
showing 10 items of 31 documents
Minimal-model for robust control design of large-scale hydraulic machines
2018
Hydraulic machines are in use where the large forces, at relatively low velocities, are required by varying loads and often hazardous and hard-to-reach environments, like e.g. offshore, mining, forestry, cargo logistics, and others industries. Cranes and excavators equipped with multiple hydraulic cylinders are typical examples for that. For design of the robust feedback controls of hydraulic cylinders, already installed into large-scale machines, there is a general lack of reliable dynamic models. Also the suitable and feasible identification techniques, especially in frequency domain, yield limited. This paper proposes a minimal-modeling approach for determining the most relevant open-lo…
Guidelines to Select Between Self-Contained Electro-Hydraulic and Electro-Mechanical Cylinder
2020
This research paper presents guidelines on how to select between self-contained electro-hydraulic and electromechanical cylinders. An example based on the motion control of a single-boom crane is studied. The sizing process of the different off-the-shelf components is analyzed in terms of design impact when replacing a traditional valve-controlled hydraulic cylinder. The self-contained electro-hydraulic solution is the best choice when a risk for high impact forces is present, when the required output power level lies continuously above 2 kW, or when installation space, weight, and cost are critical design objectives. However, the electro-mechanical solution is expected to show more control…
Classification and Review of Pump-Controlled Differential Cylinder Drives
2019
Pump-controlled hydraulic cylinder drives may offer improved energy efficiency, compactness, and plug-and-play installation compared to conventional valve-controlled hydraulic systems and thus have the potential of replacing conventional hydraulic systems as well as electro-mechanical alternatives. Since the late 1980s, research into how to configure the hydraulic circuit of pump-controlled cylinder drives has been ongoing, especially in terms of compensating the uneven flow requirements required by a differential cylinder. Recently, research has also focused on other aspects such as replacing a vented oil tank with a small-volume pressurized accumulator including the consequences of this i…
Identification and control design for path tracking of hydraulic loader crane
2017
The controlled operation of hydraulic machines with multiple degrees of freedom is challenging due to complex nonlinear dynamics of cylinder actuators, in addition to multibody dynamics like in the case of hydraulic manipulators. This paper addresses the system identification and control design for path tracking of a standard hydraulic loader crane. The kinematics of the crane is solved for operation in the vertical plane and generation of trajectories for the tool tip to be followed. A frequency response measurements and analysis have been done for dynamics modeling of both hydraulic cylinders actuating main boom and jib. The static dead-zone type input non-linearity has been identified an…
Dynamic Response of a Rigital Displacement Motor Operating with Various Displacement Strategies
2019
Digital displacement technology has the potential of revolutionizing the performance of hydraulic piston pumps and motors. Instead of connecting each cylinder chamber to high and low pressure in conjunction with the shaft position, two electrically-controlled on/off valves are connected to each chamber. This allows for individual cylinder chamber control. Variable displacement can be achieved by using different displacement strategies, like for example the full stroke, partial stroke, or sequential partial stroke displacement strategy. Each displacement strategy has its transient and steady-state characteristics. This paper provides a detailed simulation analysis of the transient and steady…
Virtual sensing of load forces in hydraulic actuators using second- and higher-order sliding modes
2019
Abstract External load forces are challenging for sensing or estimating in the hydraulic actuators. Once it is due to inconvenient instrumentation of the force sensors, especially on an open-end mechanical interface. The other way, the complex nonlinear system behavior aggravates reconstructing the system states in a robust and real-time suitable manner. This paper proposes a sensorless estimation of external load forces in standard hydraulic actuators by using a well-established equivalent output injection of the second-order sliding mode and also higher-order sliding mode differentiator. Only the basic inertial and frictional parameters are assumed to be known from an initial identificati…
Hybrid Position/Force Control for Hydraulic Actuators
2020
In this paper a novel hybrid position/force control with autonomous switching between both control modes is introduced for hydraulic actuators. A hybrid position/force control structure with feed-forwarding, full-state feedback, including integral control error, pre-compensator of the deadzone, and low-pass filtering of the control value is designed. Controller gains are obtained via local linearization and pole placement accomplished separately for the position and force control. A hysteresis-based autonomous switching is integrated into the closed control loop, while multiple Lyapunov function based approach is applied for stability analysis of the entire hybrid control system. Experiment…
Hybrid State Feedback Position-Force Control of Hydraulic Cylinder
2019
A hybrid position-force control is proposed using a unified state feedback controller in combination with feedforward dead-zone compensation. Dead-zone compensator was constructed as inverse of the identified static map while the state feedback gains were obtained using a numerical optimization routine. An accurate state-space model affine in states and control, derived in a previous work, was used for closed-loop simulations and control tuning. A trigger event for automatic switching between position and force control was defined and integrated into overall control architecture alongside with a feedforward low-pass filter reducing high frequency components in the control signal. Experiment…
A Self-Contained Electro-Hydraulic Cylinder: Modeling, Control Design, Simulation and Experimental Validation
2018
Master's thesis Mechatronics MAS500 - University of Agder 2018 In the constant effort to improve the efficiency of hydraulic systems, the pressure drop over hydraulic valves has been one of the major obstacles. In the Self-Contained Electro-Hydraulic Cylinder, the directional valve and the hydraulic power unit have been replaced by a bi-directional axial piston pump and a Permanent Magnet Synchronous Motor. Actuation of the cylinder is performed by controlling the direction of rotation and the velocity of the motor. Originally the purpose of this project was to: "Design a proper control algorithm for an existing novel selfcontained electro-hydraulic cylinder, implement it on the main boom o…
Numerical and Experimentical Study of Motion Control Using Pressure Feedback
2013
This paper is concerned with the inherent oscillatory nature of pressure compensated motion control of a hydraulic cylinder subjected to a negative load and suspended by means of an overcenter valve. A pressure feedback scheme that indirectly eliminates the oscillations is investigated. The indirect control scheme utilizes pressure feedback to electronically compensate the metering-out allowing for the removal of the compensator and, subsequently, elimination of the oscillations. The suggested electronic compensation scheme is implemented and examined in a single degree-of-freedom test rig actuated by means of a double acting hydraulic cylinder. The control scheme is compared with other con…