Base control of the modular plantation robot elWObot

Technologies in the field of mobile machinery are advancing rapidly. Today there are already different systems, that help to simplify the use of such machines and make it more secure and efficient. And this is really necessary to meet the high requirements on the quality of work, with the simultaneously predominant pressure of time. In agriculture, for example, you will find assistance systems, that take over the steering of the vehicles with help of GPS and therefore help the driver to concentrate on the work of the implement. A long-term goal is also to develop vehicles that are able to do their work all autonomously. Efforts of this kind are described by the term “mobile automation”. Because there is also a big demand for similar systems in the field of pomiculture and viniculture the chair Agricultural System Technology of Technical University Dresden, the University of Applied Sciences Osnabrück and the University of Applied Sciences Geisenheim are developing the autonomous plantation robot elWObot with electric drives. In this project, the Robot Makers GmbH is responsible for the base control of the robot.

Flexibility by four individual driven and steerable wheels

All wheels of the robot can be driven and steered individual, what results in a high flexibility. Therefore, the elWObot is able to turn around its own axis, to move sidewards or to do crab-steering. The elWObot has no driver’s cabin, but a lot of sensors, that detect the environment and therefore allow an autonomous movement. With a length of 3,20m and a width of 1,30m the robot weighs about 1600kg. Additional 2800kg can be loaded on the robot. Thus, a spray application with 1500l pesticides can be attached to the back of the robot. A diesel-engine with generator produces the necessary power for the driving motors and the implements.

The elWObot, developed by the Technical University Dresden (©TU Dresden)

The elWObot, developed by the Technical University Dresden (©TU Dresden)

Various tasks in vineyards and orchards

In the future, the elWObot should be able to do caregiving tasks in vineyards and orchards autonomously. The foundation, to reach this goal, is set by an autonomous navigation approach. Therefore, the robot is able to navigate inside the rows of trees on his own, according to his mission plan. In the next step the elWObot should be also able to handle different tasks while driving through the vineyards and orchards. These tasks include the application of fertilizers and pesticides as well as the mulching of the tramlines. Further tasks will follow in long term.

Schematic representation of the control structure of the elWObot (©TU Dresden)

Schematic representation of the control structure of the elWObot (©TU Dresden)

The Robot Makers GmbH realized, as a subcontractor of TU Dresden, the base control of the elWObot. For this purpose, the Generic Control Box comes to action to convert the default data, given by the navigation computer or the remote control, into control signals for the motor controllers. That way, the default data are converted into rotational speed and steering angle for the four individual wheels, with help of the vehicles kinematic. After the conversion is done, the data is sent to the motor controllers via CAN-Bus. Rotational speed and the steering angle of the wheels need to be coordinated narrowly, to realize clean driving maneuvers. This is due to the fact, that there is no mechanical coupling between the individual wheels of the elWObot. Normally, this mechanical coupling coordinates the wheel positions against each other. Thus, the outside wheel needs to have a higher rotational speed and a smaller steering angle, when driving along curves.

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