Tham khảo tài liệu 'sensing intelligence motion - how robots & humans move - vladimir j. lumelsky part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 36 A QUICK SKETCH OF MAJOR ISSUES IN ROBOTICS External Torques Terms 5 6 and 7 . These are due to external forces and torques that come from the arm s interaction with other objects they appear when the arm physically touches objects such as in assembly or cleaning. During a free arm motion these torques are zeros. Then there is another classification of dynamic torques also with three types Inertial Torques. These are proportional to accelerations in the arm joints and they arise from normal action reaction forces of an accelerating body. Centripetal Torques. These torques arise from a constrained rotation about a point and they are proportional to the squares of joints velocities. For example the arm s forearm must rotate about the arm s shoulder joint and so the centripetal acceleration is aimed at the shoulder joint along link 11 Figure . Coriolis Torques. These torques arise from vortical forces as a result of interaction between two rotating systems in our case two arm links and they are proportional to the product of joint velocities of two different links. Notice the remarkable growth in the complexity of equations as we proceed from kinematics to statics to dynamics equations. Then there is another natural source of complexity the arm complexity measured by the number of robot degrees of freedom. The reader is reminded that in our example Figure we are dealing with the simplest two-link planar manipulator In its analysis we started with modest kinematic equations and and arrived at rather complex dynamic equations in . Will the equations complexity grow as quickly with the growth in the number of robot DOF Indeed they will. As an example if we write only the acceleration-related coefficients for an arm with six DOF they form this 6 X 6 matrix note that a great many of today s industrial robot arm manipulators have six or more DOF D11 D12 D13 D14 D15 D16 D12 D22 D23 D24 D25 D26 D D13 D23 D33 D34 D35 D36 D14 D24 D34 D44 D45 D46 D15 D25 .
