Lecture 19
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This document discusses Denavit-Hartenberg (D-H) parameters for representing the kinematics of robot manipulators. It defines the four D-H parameters for each link of a manipulator: link length (a), link twist (alpha), link offset (d), and joint angle (theta). Conventions are presented for defining the reference frames between links based on these parameters. As an example, the document applies D-H parameters to represent the kinematics of a PUMA robot, showing the specific parameter values for each of its six revolute joints.
Lecture 19
- 1. Module 6 : Robot manipulators kinematics Lecture 19 : D-H representation of kinematics linkages Objectives In this course you will learn the following D-H Parameters of general manipulators Application to simple manipulator as example Dimentberg, Denavit, Hartenberg' s parameters of kinematics linkages: For general mechanism shown above, linkage parameters are defined as follows Common normal length between i-1 & i link is and the twist angle is . These are usually fixed parameters of linkages. The other parameters are , the offset distance between perpendiculars and , the angle of perpendiculars. Here for revolute pairs, offset distance d is fixed and its angle, is variable. And For prismatic pairs, offset distance is variable and the angle fixed. Denavit, Hartenberg' s defines the reference frames & as follows.(Conventions to be used while deciding kinematic parameters of a robot) At joint , define along joint axis and suitable to start with & & are obtained as ; take are obtained as ; Set Direction of Z axis along any +ve or –ve direction. For position of Z axis for prismatic joint à choose convenient position Choose position of common normal on 2 parallel axis, conveniently Robot is serial chain of binary links except base & EE. For reference frame on unary link, set along joint 1 axis.
- 2. Figure 19.1 These conventions are used in PUMA robot as follows (Refer figure 19.2) Example of PUMA Robot:This is all revolute pair robot as follows : Fig. 19.2 PUMA robot kinematics using D-H parameters
- 3. i ai di i 1 0 90 d1 1 2 a2 0 d2 2 3 0 90 d3 3 4 0 90 d4 4 5 0 90 0 5 6 0 0 d6 6 Set the parameters of PUMA robot as per conventions mentioned above. i.e. Set along joint 1 as shown. along axis of joint 2 along common normal. Similarly other parameters are to be set to get table shown where are joint variables. Recap In this course you will learn the following How D-H parameters are represented for general manipulator Application of D-H parameters for PUMA robot Congratulations, you have finished Lecture 19. To view the next lecture select it from the left hand side menu of the page