Mobile Robots - Moving Intelligence Part 7

Tham khảo tài liệu 'mobile robots - moving intelligence part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Design and Control of an Omnidirectinal Mobile Robot with Steerable Omnidirectional Wheels 231 rotate the wheel modules respectively. Note that the force Fi i 1 . 4 is the traction force acting on the wheel in the direction of active rolling. Using the Jacobian matrix defined in Eq. 4 the relationship between the wheel traction forces and the resultant forces acting on the robot body is given by Fr J-T Fw or Fw JT Fr 14 where Fw F1 F2 F3 F4 T and Fr Fx Fy Tz T t . It is noted that Fr is given by a vectorial sum of traction forces. Varying a combination of the traction forces can generate arbitrary forces and moments for driving the vehicle and the moment for steering the wheel modules. In addition wheel forces are given by R Fw U - Iwũ w - Cw w or R Fw U -Ặw Vw - w Vw 15 R R where R is the wheel radius U U1 U2 U3 U4 T where ui is the motor torque of the i-th motor Iw is the moment of inertia of the wheel about the drive axis and Cw is the viscous friction factor of the wheel and rnw 1 2 3 4 r where Ũ1 is the angular velocity of the i-th wheel. From Eq. 5 the wheel velocity and acceleration vectors are obtained by Vw J -1Vr Vw J -1Vr J -1Vr 16 After substitution of Eq. 14 15 and 16 into 12 the following relation is obtained R-1M nov ilv i - I T _ t-T I 1tt_ Iw T-1x7 _1_ I 1v _ cw i-1w I Í17T M r RVr RVr I J Fw J I -R U _p2 J Vr J Vr1 2 J Vr I 17 This can be simplified by use of the relation R M r R Mr to RJTMr J-1 Vr RJT R-1MrR J-1 -C J Vr U 18 1 R 1 1 R R 1 Eq. 18 represents the dynamic model of a robot. 3. CVT of OMR-SOW As explained in Section 2 a change in the steering angle of OMR-SOW functions as a CVT. The CVT of an automobile can keep the engine running within the optimal range with respect to fuel efficiency or performance. Using the engine efficiency data the CVT controls the engine operating points under various vehicle conditions. A CVT control algorithm for the OMR-SOW ought to include the effects of all four motors. A simple and effective algorithm for

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