Types of Base Bodies of Manipulators
As the number of members and the degrees of freedom of the joints connecting those increases the robotic arm can work in more complex space and orientation.
Planer: The planer base body of a manipulator can be seen as one linear manipulator attached to another linear manipulator with axes of the two manipulators being perpendicular to each other in the same plane. Thus the end of the manipulator can move along two mutually perpendicular axes and can cover all the points in the plane defined by the range of motion along the two axes. The motion of the planer base body can be defined by two variables and motion can be achieved by two linear actuators. Such manipulator has two degrees of freedom.
Examples of tasks planer manipulators can do; curve tracing or printing on sheets, metal sheet cutting for specified design, welding on a planer metal piece or drilling at different spots in a plane.
Cartesian: Such robot body allows the manipulator to move along the three Cartesian axes only, which are the three mutually orthogonal axes. The working space of such robots will be a cuboid whose dimensions are defined by the range of motion of the manipulator along each axis. Cartesian robot base consists of three prismatic joints arranged perpendicular to each other. It requires three variables to define its position, has equal number of actuators and has the same number of degrees of freedom.
One such example can be the hoisting robot used in a workshop, shipping yard or construction site which moves on rails and the hoisting hook can be moved up and down through the cables.
The types of robot base bodies discussed so far only comprise of prismatic joints and the motion along any of the axes is only linear, there is no rotary motion. Though the end effectors of a Cartesian manipulator can reach every point defined in the space but still it is not used for every purpose. It will be slow for moving between different points in the space and cannot effectively orient its end effectors properly for certain jobs. Thus revolute and cylindrical joints are included in the base body to obtain more efficient structure of manipulators.
In the next article the manipulator bases with revolute and cylindrical joints along with prismatic joints will be introduced.