HW2

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Drexel University *

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455

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Mechanical Engineering

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Dec 6, 2023

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MEM455 HW02 MATLAB FORWARD AND REVERSE DISPLACEMENT ANALYSIS HW01 uses the RobotSketch toolbox to move the robot from pose1 to pose 2 using joint interpolation. For this assignment the robot also moves from pose1 to pose2 but uses end-effector or Cartesian interpolation. A different method has to be used for a second path where the end-effector rotates in a circle. a 1 = 9.3cm, a 2 = 9.3cm, a 3 = 10.2cm. 1. Make a copy of demo_robot_serial.m and rename it to demo_robot_serial_HW02.m and similarly make a copy of demo_robot_serial_movie.m and rename it to demo_robot_serial_movie_HW02.m (a) The data files you will need should be referenced as: dh_robot_data = ’data_RRR_lab_HW02’; dh_movie_data = ’data_path12_movie_HW02’; 2. Pose1 and pose2 (from HW01) are: dh.t = [nan, 30, 45, 15, 0]*pi/180; %pose1 dh.t = [nan, 105, 45, -60, 0]*pi/180; %pose2 and all other parameters are the same as in data_RRR_lab.m 3. Write the Matlab function dh = RRR_FDA(dh) that calculates the end-effector location dh.Xe_FDA=[x e y e φ e ]. This is the Forward Displacement Analysis. Test with the pose1 joint angles. Before proceeding visually check the results by comparing with a pose1 figure. 4. Write the Matlab function dh = RRR_RDA(dh) that calculates the joint angles dh.t_RDA = [nan, θ 1 , θ 2 , θ 3 , 0] using the end-effector location dh.Xe . This is the Reverse Displacement Analysis. Test by setting dh.Xe to dh.Xe_FDA found in 3., dh.elbowplus=1 (true) , and the same dh.a (link lengths). The values of dh.t_RDA should be the same (to within roundoff) as the original pose1 joint angles dh.Xe_FDA . If not, you have an error somewhere and need to fix before proceeding. 5. It is desired to move the robot from pose1 to pose2 by simultaneously moving all joints to keep the end- effector on a straight path with a constant orientation. Write a script data_path12_movie_HW02.m to generate the end-effector locations that move the robot from [x e y e φ e ] 0 to [x e y e φ e ] n in n equal end-effector steps (giving n + 1 locations), [࠵? ! ࠵? ! ! ] = [࠵? ! ࠵? ! ! ] " + # $ ([࠵? ! ࠵? ! ! ] $ − [࠵? ! ࠵? ! ! ] " ), ࠵? = 0,1, … , ࠵?
• Use this script with demo_robot_serial_movie_HW02.m to animate the path. With the trace on, export a copy of the trajectory as path12.png . For visual clarity you may want to limit n to about 10. Also suggest you use an x − y view for to aid in analysis. 6. Repeat for a second path by writing the script data_circle_movie_HW02.m where the robot moves on a circle of radius r = 3 , always points to the center (x c ,y c ) = (3,3), has the starting end-effector angle 0 , and uses dh.elbowplus=1 . [࠵? ! ࠵? ! ! ] # = 1࠵? % − ࠵? cos 2࠵?࠵? ࠵? , ࠵? % − ࠵? sin 2࠵?࠵? ࠵? , 2࠵?࠵? ࠵? : , ࠵? = 0,1, … , ࠵? 7. Submit the following: (a) Program listings(MATLAB code). RRR_FDA , RRR_RDA , data_path12_movie_HW02.m and data_circle_movie_HW02.m. Be sure to comment your work. (b) Printout of the paths generated in 5 and 6. (Use x − y view.) (c) A short explanation comparing the results with the corresponding ones of HW1. Serial robot displacement analysis 1. For the RRP serial robot in the figure: (a) Solve the forward displacement analysis (b) Sketch another solution to the reverse displacement analysis. 2. The RPR serial robot in the figure has a 1 =a 3 =2. The end-effector location is x=2,y=4, and φ e =90 .
(a) Determine the required joint configurations (revolute and prismatic) and show them on the figure. (b) Sketch an alternative solution to the reverse displacement analysis and the actuator displacements on your sketch. (c) Determine condition(s) for a displacement singularity. If they do not exist, explain why. 3. In the study of planar robot types, why was the PPP serial robot was not studied. 4. It is physically possible for a RRR serial robot to have 360 rotation of all joints without the links interfering. Sketch a figure that illustrates this and include any constraints on the dimensions if necessary. 5. Sketch an RRR serial robot in a configuration where the reverse displacement analysis yields an indeterminate joint angle solution. What special dimensions and/or joint angles are necessary? Hint: think about displacement singularities.
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