Their joint rotation space(JRS) of both side bars and workspace of coupler points are basic issues in designing planar parallel manipulators.

According to the method of vector tube bending ,this paper deduces and compares the three algorithms about three dimensional angle of NC tube bending.

An accurate calculation method of initial backlash of the pin and cycloid transmission with teeth profile modified is presented according to the distance measured on common normal of actual teeth profile.

This paper analyzed the reason why a roller overrunning clutch idles while the driving part of the clutch is engaging,then a motion model for the idling is given,and a calculation formula of the idle angle is proposed.

By means of spherical graphics and plane trigonometry, space angle and space point coodinates are calcullated for three sets of combined fixtures as examples.

A spherical center three surface angle can be directly built in accordance with the space angle, which makes up a spherical triangle, then the space angle can be calculated using the method of calculating the spherical triangle.

There are many methods for space angle calculation in the filed of current handwork calculation, such as hexahedron, perspective geometry etc, but most of jobs in cyber-arithmetic still need further study for these methods.