Robot:Casmobot:FAQ
This page contains the archived Casmobot Frequently Asked Questions (FAQ). Please notice that the information may be outated.
What is Plant Nursing Robotics?
Plant Nursing Robotics is a Technology Transfer project, meaning that within the project realm state of the art research is applied to problems in the industrial sector. The goal is to share the research knowledge with industrial partners and thereby supporting them in their development of new innovative products.
The Plant Nursing Robotics project focuses on the development of new tools for nursing plants and green areas. The project partners are Robocluster (DK), Aarhus University (DK), VIA college (DK), University of Southern Denmark (DK), Technological Institute (DK), Design College Kolding (DK), Dvorak (CZ), Topcon - Sauer Danfoss (DE), Cetus (DK), Lynex (DK) and Datagrid (SE).
The Plant Nursing Robotics project began January 2007 and was concluded March 2009. The Casmobot project, however, still continues.
What is Casmobot?
Casmobot is an acronym for Computer Assisted Slope Mowing Robot. The Casmobot project was launched as a demonstration project within the Plant Nursing Robotics project, and the Casmobot vision is to design and develop an application module for slope mowers which enables them to perform the mowing semi-autonomous.
How does Casmobot work?
Casmobot is a robotic vehicle module that can be interfaced to existing slope mowers. Within the Plant Nursing Robotics project it is demonstrated on two remote controlled slope mowers available from Dvorak and Lynex. The Casmobot module replaces or interfaces to the existing remote control unit and hereby provides a set of computer assisted features to the user.
The features include manual driving as well as a set of semi-atonomous driving features. Manual driving may be performed using the slope mowers original remote control or another remote control unit interfaced to the Casmobot module. So far two different semi-autonomous features have been added to the Casmobot module:
- When using the line mowing feature the user tells Casmobot to follow a straight line. At eg. the left end of the grass field he by a single command tells the Casmobot to turn to the right and follow the same straight line offset by the cutting width in the opposite direction. When Casmobot reaches the right end of the grass field he tells Casmobot to turn to the left and start mowing the next line. Now Casmobot will continue mowing an increasing rectangle of grass remembering to turn by itself at the ends of the rectangle. If the user wants to increase or decrease the width of the rectangle he can easily do this using the remote controller.
- When using the area mowing feature the user steers Casmobot around the perimeter of the area to be mowed. Then he turns Casmobot to the desired direction of driving and tells Casmobot to automatically cut all grass within that area. If Casmobot during the area mowing process eg. slides down a slope leaving some grass uncut, then Casmobot will return to that location again. Large areas are segmented into smaller areas in order for the user to be able to observe Casmobot without having to move all the time.One limitation to the area mowing feature is that it can not yet handle impassable obstacles within the area.
What is the status of the Casmobot project?
The Casmobot robotics module has been interfaced to the Lynex slope mower. We are currently working on the interface for the Spider ILD2 mower.
Manual navigation using a Nintendo Wiimote has been implemented including a set of safety features to ensure that the vehicle will stop unless the user is actively controlling the vehicle.
The autonomous line mowing feature has been implemented and is working though not thoroughly tested yet. The area mowing feature has been implemented on an external computer and the first tests have shown positive results.
How does the Nintendo Wiimote work?
Interfacing the Wiimote to the Casmobot module actually started out as a funny idea one late friday afternoon in the robotics laboraty at the university. But it has turned out to be a great concept as the Wiimote seems so much more intuitive than an industrial standard remote control unit, especially to people who haven't tried steering larger remote controlled vehicles before.
The Wiimote is used like the mowers existing remote control unit, but manual steering of the vehicle is performed by simply tilting the Wiimote in the direction you want to vehicle to drive.
Is it safe to use a Wiimote for steering large vehicles? The Nintendo Wiimote is intended for playing Nintendo console games in your living room and hence Nintendo did probably not think about building industrial strength safety features into the Wiimote.
In the Casmobot project we have looked into how we could add some safety features to the Nintendo Wiimote without modifying it. Some of the main features currently implemented are:
- The Wiimote is paired to Casmobot using an internal id number within the Wiimote. You cannot just use any Wiimote.
- If the Wiimote runs out of power or simply stop working, the vehicle immediately stops.
- If the Wiimote gets out of range of Casmobot, the vehicle immediately stops.
- If you release the Casmobot "dead man" button (the Wiimote B button), the vehicle immediately stops.
- If you are not actively using the Wiimote ie. there is no motion of the Wiimote, the vehicle stops within a few seconds.
Casmobot is a prototype and it is not considered ready for sale, so in the context of this and our implemented safety features we consider the Wiimote to be safe for our purposes.
How big is the Casmobot vehicle?
The Casmobot is a robotics vehicle module that can be interfaced to existing remote controlled slope mowers. The two slope mowers within the Plant Nursing Robotics project both weigh about 300 kg and have a generator of about 25 Hp. The Lynex mower runs on belts and has a cutting width of about 1 meter, and the Spider ILD2 mower runs on wheels and has a cutting width of about 1.5 meter.
Is it safe to let a big slope mower operate autonomously?
Within the realm of the Casmobot project the safety issues regarding unmanned autonomous vehicles are not addressed. We are currently working on these issues in other research projects, but we are not yet near a solution, that is capable of providing the required level of safety.
The Casmobot is intended to drive autonomously but at all times with supervision of a user responsible for the safety of the operation. This is no different from active remote control of the vehicle except that the user needs to be attentive to the vehice even though he is not controlling it actively.
How does the Casmobot computer work?
The Casmobot computer is a Field Robotics Embedded Computer (FiRECom) from Cetus. It is an Intel compatible PC in a PC/104 form factor mounted in a dust- and waterproof cabinet. The motherboard contains a 166 MHz CPU and 128 Mb RAM. The harddisk has been replaced by a CompactFlash card in order to avoid problems caused by vibrations. Communication to sensors and actuators are handled via CAN bus, serial ports, USB and ethernet communication.
Interfaces to the slope mower actuators and sensors are handled by an Atmel AVR microcontroller card from Olimex called AVR-CAN.
FiRECom runs a version of Debian Sarge linux modified to run from a read-only drive so that the FiRECom can be turned off without having to think about file system corruption. The fact that one of the slope mowers used in the project is called Lynex is a pure coincidence and has nothing to do with the name Linux.
During the development process Casmobot has been equipped with a 3G/Wifi router for easy access to the internet and control/monitoring purposes using nearby laptops connected via Wifi.
The FiRECom and most of the software running on it was originally developed as part of the Hortibot project. The Hortibot is a tool carrier capable of killing weed in row crops using a microspray system among other things. Time Magazine has appointed the Hortibot as one of the Best Inventions Of The Year in 2007.
What is the Casmobot simulator?
The Casmobot simulator is a set of linux applications that enables the simulation of the Casmobot vehicle and sensors. Using the simulator it is possible to test software and algorithms without having to test using the slope mower all the time.
The Casmobot simulator runs as a VMware image containing the same software as the Casmobot module along with the simulator applications. In order to visualize the vehicle driving interfaces have been developed for RobWork Studio and GNUplot. RobWork is another (open source) research project from the University of Southern Denmark.
We expect to use the Casmobot simulator in future student courses at the faculty of engineering for eg. test of route planning-, controller- or sensor fusion-algorithms. Later on we expect to release the Casmobot simulator for public use, but it is not ready yet.
Interfacing to RTK-GPS, intertial and odometry sensors, position and attitude estimation using sensor fusion, wheel actuation using control theory, waypoint navigation in a 3d environment using belt or parallel driven wheel propulsion, dynamical route planning in a 3d environment, linux real-time algorithm execution.
