This paper is considering the application of a novel pump controlled cylinder drive, the so-called Speedvariable Switched Differential Pump (SvSDP), for knuckle boom crane actuation. Especially the control system for the SvSDP drive is considered, and aiming on improving energy efficiency a refinement of the existing control structure is proposed. An energy efficient sizing algorithm for the SvSDP drive is developed, and fundamental differences between the achievable operating range for the SvSDP drive compared to a conventional valve-cylinder drive are discussed. A case study is conducted with knuckle boom crane actuation, and compared to a conventional valve actuation. Simulation results show that the motion tracking performance is on a similar level compared to the valve actuation approach, while the energy consumption is drastically decreased. For the given test trajectory the valve actuation system consumes 0.79 kWh of electrical energy, while the SvSDP drive consume 0.06 kWh, if ideal energy recovery and storage is assumed.
This paper analyses the current state of the art in linear actuation with digital hydraulics. Based on the differences in their aims the paper partitions the area into four actuation concepts – parallel valve solutions, single switching valve solutions, multi-chamber cylinders, and multi-pressure cylinders. The concepts are evaluated based on accuracy and smoothness of motion, switching load, reliability, efficiency and the number of components required.
This paper is considering the analysis and control of a self-contained hydraulic winch drive. Winch drives are used in various industries, and especially in offshore and marine applications such as fishing vessels, active heave compensation applications, cranes, oil- and gas drilling rigs, vessels for wind turbine installation and so forth. When high loads are present, such winches are typically actuated by use of hydraulics, and a main disadvantage of hydraulic actuation compared to electrical actuation is the potentially large installation space required due to the hydraulic power unit. In this paper the analysis of- and control design for a self-contained hydraulic winch drive are considered. The drive includes a single supply pump, fixed displacement motor, flow control valve, a boot-strap reservoir and integrated boost-flow functionality. Emphasis is placed on the analysis of the highly coupled dynamics, an approach to decouple the dynamics and a robust control structure able to handle various types of loads aided by model reference generation. The motion performance and robustness properties are demonstrated through simulation results, when the system is subjected to a strongly varying external load and motion reference from an offshore wind turbine blade installation system.
This article aims to analyze Model Predictive Control (MPC) for the control of multi-chamber cylinders. MPC with and without integral action has been introduced. Three different algorithms have been used to solve the optimization problem in the MPC. The different algorithms have been compared with an industrial solver. The influence of changing mass, choosing a different middle line pressure, system delays, signal noise, velocity estimation, and changing pressure levels has been investigated. It is concluded that for the small prediction horizon used in the paper a simple algorithm such as A * can produce results as good as the previously used Differential Evolution algorithm in less than half the time. It is further concluded that unknown software delays and unknown changes in mass have the largest effect on system performance.
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