Rexroth Bosch Group HNC100 Hydraulic Shaft Control

It is worth noting that the WIN-PED software (model SYS-HNC-WINPED5-C01) is not included with the controller, but can be downloaded for free from the Bosch Rexroth official website or ordered in CD-ROM format. This strategy ensures that users can always use the latest version of the software.

Deep analysis of core control algorithms: not just PID

The strength of HNC100 lies in its specially optimized controller library for hydraulic shaft characteristics. The inherent nonlinearity of hydraulic systems, such as friction, oil compressibility, and dead zone characteristics of valves, often makes it difficult for standard PID controllers to achieve ideal results. HNC100 provides multiple advanced control strategies to address these challenges.

1. Position controller:

Type: PDT1 controller. This is a proportional controller with differential and delay elements, which is very suitable for hydraulic systems with large inertia or pure integral characteristics.

Nonlinear gain: Supports direction dependent gain adjustment and "inflection point" gain characteristics. For example, different proportional gains can be used when moving up and down to compensate for the influence of gravity.

Fine positioning: Provides the principle of "residual voltage" and zero error compensation function, effectively eliminating crawling and positioning dead zones caused by static friction, achieving micrometer level positioning accuracy.

State feedback and feedforward: supports state feedback control, which can improve the damping ratio of the system; Simultaneously providing Command value feedforward significantly reduces tracking errors and improves dynamic tracking accuracy.

Position related braking: This is a very practical function that can automatically generate a deceleration curve based on the distance from the target position, achieving smooth and accurate stopping, avoiding impact and overshoot.

2. Pressure/Force Controller:

Type: PIDT1 controller.

Feature: The I component (integral) can be cut in and out through a window function. For example, when the pressure error is large, the integration function can be turned off to prevent integration saturation; When the error enters the window, activate the integration function to eliminate the static error.

Differential pressure assessment: capable of processing differential pressure signals to improve system response speed.

Independent scanning cycle: The scanning cycle of pressure control can be different from that of position control to adapt to the characteristics of pressure signals that usually change faster or require faster response.

3. Speed controller:

Type: PI controller.

Feature: It also supports window entry/exit function for integral components, ensuring steady-state accuracy while preventing integral saturation.

4. Advanced control functions:

Alternating closed-loop control: This is an extremely important function in hydraulic systems, and its typical application is "position pressure" alternating control. For example, during a pressing process, the HNC100 can first rapidly feed in the position closed loop, seamlessly switch to the pressure closed loop for pressing when in contact with the workpiece, and then switch back to the position closed loop for return after the pressure holding is completed. This gentle switching requires extremely high performance from the controller, and HNC100 provides dedicated support.

Synchronisation control: used for synchronous movement of two hydraulic shafts, such as synchronous lifting platforms or large sliders driven by dual cylinders. The controller can dynamically adjust its control output based on the real-time position difference between the two axes to maintain synchronization accuracy.

Electronic cam (Curve function): By using NC commands such as KURVE, an electronic cam curve defined by a polygon can be activated to achieve nonlinear position synchronization between the master and slave axes.

Practical NC Programming: Defining Machine Motion with Code

The programming language of HNC100 is a typical motion control language, and engineers familiar with G-code can quickly get started. Its command set is divided into several key parts:

Sequence control:

G01: Linear interpolation (point-to-point motion) is a fundamental motion command.

G30: Point to point motion optimized for oscillatory motion.

G26/G25: Limit block approximation with closed-loop/open-loop control. G26 precisely presses against a mechanical stopper through closed-loop control and can stop after reaching the set pressure, which is a standard action in many press fit applications.

G60/G61/G62: Activate pressure controller, activate pressure limit, cancel pressure limit. This makes it possible to dynamically switch control modes based on conditions during movement.

Logic and Control Flow:

IF, JMP, JSR, M17, M02: Provides complete program flow control capabilities such as conditional branching, unconditional jumping, subroutine calling, subroutine termination, and main program termination.

M00, G04: Waiting for input signal or delay, used to coordinate external device actions.

Parameters and Variables: