Platform for Simulated Helicopter Motion
3DOF (Pitch, Roll, & Yaw)
Rear view of the 3DOF main support platform with universal joint/roller bearing hub assembly.
The universal joint allows movement for "pitch and roll" axis positions.
On top is the rotating hub which allows for the "yaw" axis (tail rotor control) movement.
Truck universal joint with the hubs' spindle welded in the top center of the universal joint flange.
The universal joint came from a vehicle wrecking yard, the heavy duty hub and spindle from a farm implement supply.
Pitch and roll control arms (3" steel channel) welded to top universal joint flange.
The simulator sits on this welded steel frame,
which bolts to the rotating hub, which defines the yaw axis pivot point.
This linear actuator will be tested as a possible drive system for the pitch, roll, and yaw axis control motion.
The 12 volt linear actuator has a 10:1 gear ratio, ball bearing screw, and a 12" stroke.
Yaw Axis
(Left) An offset mounting bracket for the linear actuator was fabricated and bolted to the extended pitch control arm.
(Right) The shaft of the linear actuator is attached to the pivoting yaw frame with a small universal joint.
Photos show linear actuator yaw positions to right and left.
Pitch Axis
In order to mount the actuator inside the frame, a ball bearing equipped jackshaft was installed, to accommodate the length of the linear actuator and redirect the output direction from horizontal to vertical. This jackshaft connects the pitch axis control arm to the linear actuator.
Roll Axis
This jackshaft connects the roll axis control arm to the linear actuator.
To see this video of the roll axis drive you will need Shockwave Flash Player. In the video the motor is operating from a 12V battery with no weight to push around. Once the simulater is mounted and balanced it will be switched to an 18V power supply for further tests. Time will tell, but I'm hoping to get enough power and speed for practical 206 helicopter flight characteristics.
This board contains the DC motor controllers and relays for controlling the pitch, roll, and yaw motors. The motor controller circuit boards are connected to the flight computer with two USB cables. In this photo, the "emergency" master power switch is located on the front left side of the board, but this switch will be moved to the inside of the cockpit once final setup and testing is started.
Position Sensors
These are the position sensing potentiometers that keep track of where the pitch and roll axes are at any given time.
The potentiometers are driven with a ball bearing supported plastic timing pulley. A short length of timing belt, which has one end attached to the axis control arm, drives the pulley. A tensioning spring on the other end of the belt keeps it tight. This system helps prevent any "backlash" that might occur with other types of gearing, or lever type attachment points to the potentiometers.
The motion platform is now installed under the cockpit for final balancing and testing.
Balancing is critical to this type of design, to help allow the motors to handle the extreme platform positions.
For a single occupant (pilot only) weights are placed under the passenger seat to help with balancing.
All three linear actuators have been installed to the motion base frame.
