Digital displacement control for hydrostatic pumps - Mobile Hydraulics - Denison Hydraulics

Diesel Progress North American Edition, July, 2003

Denison Hydraulics has developed a new family of digital electronic controls designed to provide high performance and efficiency at a low cost. Most recently, the company hunched its new Denison Hi-IQ control for the GoldCup series of variable displacement, axial piston, closed-circuit, hydrostatic pumps targeted toward applications such as marine winches and cranes and cement making machinery.

The GoldCup Hi-IQ units can drive either hydraulic cylinders or hydraulic motors in closed-loop positioning or speed control systems. Applications currently using high flow proportional and servo valves in closed-loop motion control systems are good potentials for the GoldCup Hi-IQ, according to the company.

The control system consists of: a GoldCup series P6 - P30 axial piston pump with integral displacement sensor; a high response 4DCO1 proportional directional control valve with integral LVDT; and an ECO1 digital electronic controller in Eurocard format. A key element of the system is the EGO 1 digital control card, which incorporates a 16-bit SAB 80C166 microprocessor.

The system includes six analog and eight digital inputs, along with two analog and four digital outputs. Both RS232 and CAN-Bus serial ports are provided.

The modular construction concept of the ECO1 Family connects a digital controller sub-board to a standard basic amplifier card. The electrical connections to the ECO1 are in accordance with typical industry standards, the company said.

The displacement of the GoldCup P6 - P30 pump is controlled by a high-performance, closed-loop, proportional valve mounted directly on the pump. An electrical signal is also supplied to the controller from an integral position sensor that measures the actual displacement of the pump. The customer-supplied input command for displacement is continuously compared to the actual pump displacement and the pump regulator provides a signal that is proportional to the difference between the input displacement command and the actual displacement. This error signal provides the input to the valve regulator.

The output stage of the valve regulator then delivers the high power signals to both of the proportional solenoids to move the valve spool to minimize the error.

A Windows-based communication software package is available to allow customers to configure, tune, and monitor the operation of the Hi-IQ pump control system with a standard personal computer. This software uses the standard RS-232 serial port of the PC to communicate with the ECO1.

With these tools, the time required for installation and commissioning of the control system has been dramatically reduced, Denison said. The customer can store the electrical connection information, control parameters, and calibration data in nonvolatile memory on the ECO1 card and also in back-up files on a PC (i.e., 24 V power supply, current or voltage input command signals, and a maximum current consumption of 3 amps).

The new controls were developed at Denison's Hilden, Germany facilities. Denison's piston pumps are manufactured in Marysville, Ohio. *

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