Wii-like Controller by Paul Tingey

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Wii-like Controller by Paul Tingey

NXT Arm Wii-mote using Mindsensors compass & accel sensors
Paul Tingey has created this contraption, which functions like Wiimote. It uses CMPS-Nx and ACCL-Nx-3g3x for gathering the spacial orientation of the controller. This data is used by the RoboArm T-56 to re-orient it's arm.

The wii-like remote is a spatial remote control used to control the motors on the NXT Roboarm T-56. It is held like a normal candy bar remote and has a touch sensor which is pressed via a thumb operated lever. While the button is pressed, any movements by the remote in 3D space are measured and used to set the amount of power applied to the arm's motors. Tilting forward and back is sensed by the accelerometer's x-tilt register which controls the arm's extend/contract motor. Tilting left and right is sensed by accelerometer's y-tilt register which controls the gripper's open/close motor. Twisting clockwise and anti-clockwise is sensed by the compass's heading register which controls the arm's left/right turning motor. When the button is released the motors are switched off.

While pressed, the power applied to the motors is proportional to the change in the remote's position relative to when the button was first pressed. More specifically, when the button is pressed the current value of each register is recorded. The registers then are polled periodically and on each cycle the difference from the initial value (the delta) is calculated. If a delta is larger than a threshold value, it is scaled, clipped, and applied to one of the motor's power settings. This continues until the button is released. A large movement will cause the motor to be driven with more power and run faster. Each axis/motor has a different threshold and scaling value. The deltas are prioritised so only one action takes place at a time, in the order; x-tilt, y-tilt then compass headings. This is needed because the compass can give incorrect readings when tilted too far. Special treatment is also applied to the gripper which has limited gearing. A short blast of power is sufficient to make it reach its limits. The tachometer on the gripper's open/close motor is used to stop it going beyond its open/closed limits.

The next step will be to make a model what can apply the remote's deltas directly to a rotation count or tachometer reading rather than a power/speed setting. This will require a simpler model that can respond fast enough to make it fun! The wii-like remote is quite a simple application but shows what powerful things can be done with the Mindsensor's acceleration and compass sensors.
You can see more pictures here.

LEGO NxtShot 2.0 - cannon using Acceleration Sensor

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