For large property owners, routine maintenance like mowing and snow removal are ongoing and time consuming. A machine that could perform a portion if not all of these tasks autonomously would free up considerable time and conceivably use less fuel for the same task. Production costs may also be reduced by eliminating the need to accommodate a passenger.
Having a hardware platform to develop software is desirable, in some cases, over simulation and is the motivation for building this computer controlled skid steer robot.
Hydraulics and internal combustion engine combination were selected for practicality, power and run duration.
Drive wheels are independently chain driven (left and right) utilizing hydraulic motors with high resolution magnetic encoders. A dedicated microcontroller receives the encoder position signal and in turn adjusts a hydraulic valve to maintain a programmed speed and duration using closed loop PID algorithms. Variances in speed allow turning the robot without a complicated steering mechanism.
Lift arm and end effector angle are controlled in a similar way as the drive wheels using hydraulic cylinders and high resolution magnetic angle sensors with a dedicated controller using closed loop PID. The bucket in this example is only one of several interchangeable end effectors for various tasks that will also include a gang reel mowing deck and possibly a snow blower.
All dedicated controllers receive commands in standard ASCII over RS-232. Once the controller receives the command, no more input is needed to complete the motion. A more powerful onboard computer coordinates the motion and can function independently with no other external input. Manual control is achieved through a simple SSH connection using an onboard router.
With this platform, simple software drivers can be written to integrate with ROS (RobotOS). This will allow virtually any sensor to be added to assist navigation, obstacle avoidance, route planning, machine vision, machine state monitoring and more.