This paper addresses the problem of autonomous control of a hydraulically actuated articulated-frame-steering (AFS) mobile machine— a wheel loader. Our autonomous motion control system includes a mission planning graphical user interface, an improved odometry algorithm and a GPS device for navigation purposes, together with a model based path-following control strategy, and speed control. The test platform is a small prototype wheel loader based on Avant-635 whose hydraulic components are substituted by electrically controlled equivalents. System development and preliminary calibrations are done using GIMsim— an elaborated semi-empirical hardware-in-the-loop simulator. Some field experiments are presented that demonstrate satisfactory performance of the system at this stage. Further tunings are required to reach a desired performance.

Abstract-Attachments and their controls can be connected to hydraulic mobile machines in different ways. The traditional approach is to install hydraulic valves of the attachment close to the operator. Thereby levers of the valves can be reached from the operator seat. This, however, restricts the size and number of the valves and can be inconvenient for the operator. A more advanced and ergonomic way is to use electronic control which allows installing the valves more freely on the attachment. The operator can then control the attachment with a joystick, for example. Usually there is a microcontroller unit in an electronically controlled mobile machine. One solution is to use this unit to read the joysticks and output control signals to the valves of the attachment. However, if there is a microcontroller in the attachment as well, the wiring can be minimized and the attachment can perform intelligent functions, for example positioning, as the machine sends simple commands. The data transfer between the microcontrollers can be realized flexibly and reliably using a serial bus such as CAN.A hydraulically operated excavator for a hydraulic mobile machine is discussed as an example. The excavator has four PWM controlled spools in a sandwich type proportional mobile valve. A suitable microcontroller is chosen to interface the valves of the excavator to the CAN bus of the mobile machine. Different command sets and levels of intelligence are deliberated. Adding different types of sensors to the excavator is concerned. The sensors are used to achieve more accurate, independent and safe operation. The microcontroller unit is designed to have extra interfaces for future research with different sensors. The unit is designed, built and installed to the excavator. The design of electronics and software is presented in this paper. The excavator is attached to the hydraulically operated mobile machine and the performance of the system is tested. The test arrangement is described. The results are presented and discussed. IndexTerms-CAN, intelligence, mobile machine, proportional valve. O. I. Karhu is with the Institute

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Autonomous functions are a common research topic in robotics. However, the robots typically have limited operating conditions and they can only handle relatively small loads. Many autonomous control concepts are applicable to actual construction machinery. The benefits would be considerable regarding efficiency, safety, and operator comfort. The research projects of this field have often led to systems with cost and complexity too high for most applications. This paper presents an implementation of a cost-effective distributed control system that is retrofitted to a small hydraulic excavator. The system can be used to perform simple operator assisting functions but also to develop autonomous excavation. The hardware of the system consists of cost-effective joint angle sensors and a flexible microcontroller unit. Control schemes that produce autonomous functions are discussed and tested with the excavator. These include position controllers for conventional mobile proportional hydraulics. The aim is to find computationally simple but flexible algorithms for autonomous excavation. The results of the preliminary tests are presented. Future improvements are discussed.

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