Julian Cendrowicz

A concept of digital control system to assist the operator of hydraulic excavators

Abstract A concept of digital control system to assist the operators of hydraulic excavators is presented and discussed. Then, control system based on described ideas was mounted on a special numerically controlled stand, equipped with D/A and A/D converters, where small hydraulic backhoe excavator K-111 fixtures were used. Experimental results shows that it fulfils all described requirements and can be used as the machine operator assist. It enables for precision tool guidance, automatic repetition of realized movements, realization of specific tool trajectories (including energetically optimal paths) and automatic improvement or optimization of realized paths. Tool trajectories can also be prescribed using the setting model, making excavator the machine of teleoperator class. Presented system can be used as a basis for real machine control system.

Digital Control System to Generate Energetically Advantageous Cutting Tool Trajectories for Hydraulic Excavators

The computer control system for the backhoe hydraulic excavator is presented and discussed in the paper. It can be used to help the operator during the shoving process to generate energetically advantageous trajectories obtained as automatic tool leading along the previously generated slip lines. The results of experiments, carried out for the loading type kinematics under the plane strain conditions and for the bucket with side walls, confirm the efficiency of such trajectories. Experimental results for K-lll backhoe excavator are also presented here. It is shown, that the automatic system enables the realization of tool trajectories with proper precision.

A Digital Control System for Hydraulic Excavator Fixtures

533 The cutting tool trajectory of a hydraulic excavator during working with traditional machine results from experience and intuition of an operator. To allow the excavator for an automatic execution of planned trajectories, the machine should be provided with control system of fixtures motion. Such a digital control system for single bucket excavator, which has been built in the Kielce Branch of the Institute of Fundamental Technological Research of Polish Academy of Sciences, is presented in this paper. 1. DESCRIPTION OF THE SYSTEM AND THE TESTING STATION The determination of tool coordinates in assumed coordinate system in real time is necessary for execution of tool motion along the assumed path. For machines of an excavator type it can be made indirectly by measuring of the cylinder position or the angular orientation of fixtures. Such an idea was used to built in IFTR the model control system for excavators, where signals from position sensors of cylinders or angular sensors of fixtures are used as feedback signals for regulators. The system is based on PC/486 computer provided with analog-to-digital and digital-to-analog converters with control procedures built on the basis of interruption system with minimal possible sampling period of 5ms. The system called DIGDIGG (Digital Digger) allows [1,2,4] for: • manual control with stabilization of fixtures position, • real time animation of fixtures on monitor display, • regulation of cylinders position or fixtures angular positions by means of PID controllers or state controllers, also with state observers, • identification of control plants and selection of optimum parameters for digital controllers, • various methods for planning of the cutting tool trajectory, • modification of the trajectory during motion, what allows for obviating of obstacles, • optimization of the cutting tool trajectory, • measurement of forces acting on cutting tool of excavator, • observation of an experiment and documentation of its results. The special testing rig was built for examination of the mentioned-above system [4]. Its working part consists of fixtures for single bucket hydraulic back digger with bucket