求机械专业的英文的文章翻译 《翻译软件的闪》
Workspace considerations, particularly reach and collision avoidance, play an important part in the selection of a robot for an application. All manufacturers give detailed specifications of the work space of their robots and associated equipment.
Consideration of the motions involved in assembly has led to the development of a simpler arm geometry for use in assembly applications, known as the SCARA (Selective Compliance Automatic Robot Arm) geometry. While all SCARA robots have the same geometry the name SCARA does not have a geometric basis. Most assembly operations involve building up the assembly by placing parts on top of a partially complete assembly. A SCARA arm has two revolute joints in the horizontal plane, allowing it to reach any point within a horizontal planar workspace defined by two concentric circles. At the end of the arm is a vertical link which can translate in the vertical direction, allowing parts to be raised from a tray and placed on to the assembly. A gripper placed at the end of this link may be able to rotate about the vertical axis of this link, facilitating control of part orientation in a horizontal plane. The kinematic structure of the robot arm allows to postion its end point at any (x,y,z) location in
the 3D space (…. within the robot's working space)
In order to provide for the proper orientation of the hand/end-effector the robot arm should have a wrist. Typically a robot wrist provides the same 3D rotations as a human hand: roll, pitch, and yaw. A wrist where the three axes of rotation intersect is called a spherical wrist. These have the advantage that the mathematical model used to calculate the wrist joint angles from their position and orientation in space is soluble.
One problem in achieving spherical wrist design is the physical difficulty of fitting all the components into the available space. The size of the human wrist is small because the muscles which power it are located in the forearm, not in the wrist. Wrist design is a complex task, involving conflicting goals. Desirable features of a wrist include :
-small size
-axes close together to increase mechanical efficiency
-tool plate close to the axes to increase strength and precision
-soluble mathematical model
-no singularities in the work volume
-back-driving to allow programming by teach and playback
-decoupling between motions around the three axes
-actuators mounted away from the wrist to allow size reduction
-paths for end effector control and power through the wrist
-power proportionate to the proposed task
-rugged housing.