Lander Control and Sensing Unit

The models visual presentation of flight simulation relies on the combination of the two major motions - Vertical movement of the Lander Module (LM), and Horizontal movement of the Landscape.

In order for this to work, the model needs to know exactly how the LM is oriented so that it can work out how much thrust to apply in each plane, and in which direction. 

Key to achieving this objective is the LCASU (Lander Control And Sensing Unit) see images below.

The Lander Module Rotation Motor is built into this unit. The first driven shaft has a crank assembly to the rear which operates a pair of ganged sliding potentiometers. These need to run full range twice for every full rotation of the Lander. The reasons for this will become clear shortly.

A 2:1 reduction gear then passes the drive down to the main shaft which extends to the lower end of the Vertical movement tower. Here, the drive is carried up to the final output shaft on which the Lander Module is mounted. The final shaft is carried at the top corner of a pantograph assembly, and a chain drive transmits LM rotation drive from bottom to top, regardless of the altitude of the LM.

The pantograph assembly and LM assembly will be shown in another section to follow later.

Back to the LCASU however, the main output shaft carries 3 sensing cams each of which operate a limit switch. Two of the cams are semi-circle plates set at 90 degrees to each other. One detects LEFT/RIGHT orientation, and the other detects UP/DOWN orientation. The third cam is a collar which detects if the LM is upright or not, within a fairly tight tolerance. Signals from the semicircle cam switches are sent to the thrust circuits to control the thrust demand motors in the correct sense. The degree of thrust is controlled by the sliding pots, so that as the LM attitude changes from fully Vertical to fully Horizontal, the thrust signal is phased from one main drive to the other. 

When fully upright, (zero degrees) 100% thrust goes to the Vertical demand motor, in the UP direction.

After 90 degrees rotation (clockwise say) the LM faces right, and 100% thrust goes to the Horizontal demand motor, in the RIGHT direction.

Continuing to 180 degrees, the LM is now pointing down, an 100% thrust returns to the Vertical demand motor, but at 90 degrees the direction has already switched from UP to DOWN.

This constitutes one full rotation of the crank, and full range of the sliding pots in both directions.

The output voltage of each pot is fed to a PWM driver, one for each demand motor. This is how the speed control is phased from one plane to the other during the transition from 0 - 90 - 180 - 270 - 0 degrees of angular orientation (attitude).

What the demand motors then do is covered in the section on VSD's (Variable Speed Drives)

A schematic VirtualMec drawing of the LCASU and pantograph drive up to the Lander is shown for clarity.

A further few images of the device are also shown for the cams, switches and sliding pots. 

There is also a disconnect mechanism built in to allow the LM to be positioned manually during the game set up/reset process.