For highest performance and precision, use closed-loop control

12 July, 2018

Cylinders, valves, pumps and accumulators used in closed-loop systems must be sized large enough to allow for quick acceleration and positioning of the actuator. Hose runs should be short, and metal tubing should be used where possible, with as few bends as possible, in order to reduce the amount of fluid compression and expansion which can affect controllability.

Programming and tuning the motion

Key to setting up the motion is the application development tool set. In the case of Delta Computer Systems’ motion controllers (an example is the RMC200 shown in Figure 2), that tool set is the RMCTools package, provided free with the company’s controller products. Rather than requiring the use of low-level machine code as is the case with many other motion controllers, this development environment includes graphical tools for programming, troubleshooting, and tuning motion algorithms. RMCTools allows motion sequences to be set up by filling out forms and selecting intuitive options from pull-down menus (See Figure 3).

Once the motion steps are programmed, the system must be tuned for optimal operation. For this step of the development process, the RMCTools package provides software for analysing the motion and adjusting control loop gains. The software contains a Plot Manager for displaying motion parameters versus time, and a Tuning Wizard (Figure 4) to simplify the tuning process.

Hydraulics advantages summarised

Hydraulic motion control offers many benefits over electric motor control, especially when working with high-speed linear travel, heavy loads or when very smooth position or pressure/force control is required. By selecting appropriate system components and programming your motion controller to use the correct closed-loop motion control algorithms, the result can be a system that offers high performance and very precise motion at a reasonable cost.