AUTONOMOUS ROBO CONTROL USING CAN PROTOCOL
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Joined: Sep 2010
09-10-2010, 02:36 PM
The aim of the project and implimentation is to develop an embedded robot which is an autonomous using CAN protocol.
In the present project and implimentation we are demonstrating the applications of the CAN protocol in the robot Automation. Here we are designing an embedded robot which will be controlled according to the ultra sounds emitted by ultrasonic sensors .If there any reflection of the ultra sounds by the obstacle then immediately our robo will change the direction .This makes the robot an autonomous. The ultrasonic sensors are connected to one microcontroller and the motors are connected to the other microcontroller. If any obstacle is detected by one microcontroller then it sends signals to the other microcontroller. This communication is though CAN protocol .
CAN is a multi-master broadcast serial bus standard for connecting electronic control units (ECUs).
Each node is able to send and receive messages, but not simultaneously: a message (consisting primarily of an ID usually chosen to identify the message-type/sender and up to eight message bytes) is transmitted serially onto the bus, one bit after another this signal pattern codes the message (in NRZ) and is sensed by all nodes.
The devices that are connected by a CAN network are typically sensors, actuators and control devices. A CAN message never reaches these devices directly, but instead a host processor and a CAN controller are needed between these devices and the bus.
If the bus is free, any node may begin to transmit. If two or more nodes begin sending messages at the same time, the message with the more dominant ID (which has more dominant bits, i.e., bit 0) will overwrite other nodes' less dominant IDs, so that eventually (after this arbitration on the ID) only the dominant message remains and is received by all nodes.
Each node requires
• a host processor
o The host processor decides what received messages mean and which messages it wants to transmit itself
o Sensors, actuators and control devices can be connected to the host processor (if desired)
• a CAN controller (hardware with a synchronous clock)
o Receiving: the CAN controller stores received bits (one by one) from the bus until an entire message is available, which can then be fetched by the host processor (usually after the CAN controller has triggered an interrupt)
o Sending: the host processor stores its transmit messages into a CAN controller, which transmits the bits serially onto the bus
• a Transceiver (possibly integrated into the CAN controller)
o Receiving: it adapts signal levels from the bus to levels that the CAN controller expects and has protective circuitry that protect the CAN controller
o Sending: it converts the transmit-bit signal received from the cAN Controller into a signal that is sent onto the bus.
Bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Decreasing the bit rate allows longer network distances (e.g. 125 kbit/s at 500 m).
The CAN data link layer protocol is standardized in ISO 11898-1 (2003). This standard describes mainly the data link layer — composed of the logical link control (LLC) sublayer and the media access control (MAC) sublayer — and some aspects of the physical layer of the OSI reference model. All the other protocol layers are the network designer's choice.
1. Embedded C
2. Keil IDE
1. Micro Controller
2. MCP 2515 can controller with a driver
3. Power supply
4. ULTRASONIC SENSORS
5. DC motor
So from this project and implimentation we can implement autonomous robot control using CAN protocol.
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