Tham khảo tài liệu 'advances in robot navigation part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Distributed Mobile Robot Navigation by Snake Coordinated Vision Sensors 189 2. Control token negotiation At a specific time one robot should be controlled by only one vision sensor. All vision sensors which have the robot in view will compete for the token. The vision sensor with a control token will become the dominant vision sensor and broadcast its ownership of the token periodically or initiate a token handover procedure if required 3. Mobile robot control The dominant vision sensor sends control to the robot the one without a control token will skip this step 4. Monitoring purpose reporting If a vision sensor is marked by an operator to send monitoring related information such as control points it will send out the corresponding information to the remote console. Protocol stack structure The proposed control protocol is built on top of the IEEE protocol which has the following data structure Zhang 2008 typedef struct_TOS_Msg __u8 length data length of payload __u8 fcfhi Frame control field higher byte __u8 fcflo Frame control field lower byte __u8 dsn sequence number __u16 destpan destination PAN __u16 addr destination Address __u8 type type id for Active Message Model handler __u8 group group id __s8 data TOSH_DATA_LENGTH payload __u8 strength signal strength __u8 lqi __u8 crc __u8 ack __u16 time TOS_Msg As seen in the TOS_Msg structure 16 bytes are used as headers the maximum payload length TOSH_DATA_LENGTH should be 112 bytes. The control protocol packets are encapsulated and carried in the payload. The protocol stacks at different interfaces are discussed in the following subsections. Protocol stack between vision sensors As shown in Fig. 6 the control protocol layer is built on top of the physical lay and MAC layer of the protocol stack to enable vision sensors to communicate with each other. The information processing and robot navigation control algorithms are resided within the control protocol layer. 190 Advances in Robot
