Development of Point-to-Point Path Control in Actuator Space for Hydraulic Knuckle Boom Crane

Abstract

This paper presents a novel method for point-to-point path control for a hydraulic knuckle boom crane. The developed path control algorithm differs from previous solutions by operating in the actuator space instead of the joint space or Cartesian space of the crane. By operating in actuator space, almost all the parameters and constraints of the system become either linear or constant, which greatly reduces the complexity of both the control algorithm and path generator. For a given starting point and endpoint, the motion for each actuator is minimized compared to other methods. This ensures that any change in direction of motion is avoided, thereby greatly minimizing fatigue, jerky motion, and energy consumption. However, where other methods may move the tool-point in a straight line from start to end, the method in actuator space will not. In addition, when working in actuator space in combination with pressure-compensated control valves, there is no need for linearization of the system or feedback linearization due to the linear relationship between the control signal and the actuator velocities. The proposed solution has been tested on a physical system and shows good setpoint tracking and minimal oscillations.

Novel Concept for Electro-Hydrostatic Actuators for Motion Control of Hydraulic Manipulators

“…Hence, components and control parameters are quantified and the concept is evaluated via time-domain simulations. The simulations are performed using an outer path control loop with anti-swing which have been developed earlier in [27,28]. The novel concept has also been compared with a traditional design with a single pump driven by an induction motor and proportional valves to control each actuator.…”

“…To test the performance of the developed system, numerical simulations are carried out with path control and anti-swing as a load case. Path control and 2-DOF anti-swing have previously been developed in [27,28]. An illustration of the HMF 2020K4 crane with hanging load is shown in Figure 26.…”

Development of 3D Anti-Swing Control for Hydraulic Knuckle Boom Crane

“…The main task is position control of the tool point and, classically, this may be combined with a velocity feedforward term. Feedback control is most easily implemented in actuator space Jensen et al (2020b). Therefore, inverse kinematics is used to transform from tool point coordinates via joint coordinates to actuator coordinates.…”

“…The control of the hydraulic cylinders uses feedback of the position error, and feedforward based on the velocity reference. Since the hydraulic system yields load independent velocity control, feedforward is an effective control method, as stated in Bak and Hansen (2013) and Jensen et al (2020b). The anti-swing gain k a and the payload angles α and β are used to generate two anti-swing crane tip velocities, ẋt,a and ẏt,a in order to suppress the payload angles.…”

“…For the simulation, a path controller based on a trapezoidal velocity reference is used, as described in Jensen et al (2020b). The path controller operates in actuator space, and uses segments of constant cylinder velocity.…”