Six-Axis Manipulator for an Accelerator End-Station

The 15-degree end station of the 1.7MV tandem Pelletron accelerator features a six-axis target and detector positioning system with stepping motors controlled by physical switches. The target is positioned via three linear axes (x, y, and z) and two angular axes (θ and ϕ), while the sixth axis controls the angular position of the detector. However, the ϕ-axis motor for the target has no control switch, so it can’t be operated (it once had a serial connection to be operable by computer). Besides an external ruler for the z-axis, the current motor manipulator system has no method to determine motor positions; users can merely shine a flashlight through an observation port to estimate the resulting positions. To enhance repeatability and precision, a remote six-axis control system was developed using LabVIEW. The computer interface controls two three-axis Trinamic motor control modules and reports final axis positioning to the operators on screen, graphically and numerically. Users can save and restore prior configuration states across all six axes. Additionally, a new electro-mechanical switching box with six switches has been developed to be compatible with the Trinamic control modules. The new switch box uses separate onboard I/O control chips on the Trinamic modules so that they can be operated even when the computer controller is not active. The new switch box includes 4 indicators for each axis (“moving forward”/”moving backwards”/”at the front limit”/”at the back limit”), where the existing system only had one indicator per axis (“on”/”off”). The circuitry and code for the new switchbox is designed to prevent users from requesting invalid motions of the stepper motors, and to prevent simultaneous motion of more than one axis. To test the new control system, a 3D printed physical model simulating the existing six-motor system with limit switches was created and tested, using both the onscreen (LabVIEW) control system and the new physical switchbox.