using SINE function for cylinder positioning

[thoresonr]

Friends, I have a CP1H 40-xa-dt monitoring and positioning a hydraulic cylinder. The HMI I am using is a NB5Q. As of right now, LVDT position is wired directly to a Parker BD98A servo card which looks for input voltage with respect to the positive and negative terminals to determine output in positive/negative direction. (eg. positive voltage on IN6 vs IN7 provides positive current on OUT1 vs OUT2, positive voltage on IN7 vs IN6 provides positive current on OUT2 vs OUT1). My Issue is that the LVDT only operates in a positive voltage direction. I've wired up a relay to switch the wired terminals as an experiment and it works, but the LVDT voltage goes from a maximum positive to a maximum negative voltage to input terminals and the cylinder slams retracted. I know the CP1H can be scaled -10 to 10vdc on the D/A terminals. Could a SINE function be used so the cylinder will follow sine wave and extend while riding the curve in positive direction and retract once sine wave is below 0 in the negative direction? If this is possible can i control the speed of operation, like using an increment function? The cylinder is only being tested for operation for a certain amount of time to ensure no leaks after rebuild. I am a bit new to this. Regards, Thor