Cyclic/collective pitch mixing
Used in radio-controlled helicopters, Cyclic/collective pitch mixing (CCPM) reduces mechanical complexity and increases precision of control of the swashplate.
Conventional model helicopters use three independent servos to manipulate the swashplate. All three servos are used in varying amounts (i.e., mixed) to tilt the swashplate forward and aft (longitudinal cyclic), varying the aircraft's pitch, left and right (lateral cyclic) and varying the roll. All three servos equally raise and lower the entire swashplate, varying the collective and hence the pitch of the rotor blades. An intermediate mechanical mixing system is used to transfer the control inputs from the servos to the swashplate. This requires an elaborate system of control rods and levers, which often contains many ball bearings.
To reduce the mechanical complexity of the helicopter, a CCPM system mixes the control inputs using software (usually running on the transmitter) and typically uses three interdependent servos to control the swashplate, with three linkages arranged around the swashplate at 120° intervals (there is a variation that uses 140° + 140° + 80° intervals). In addition to lower mechanical complexity, the interdependent servos share the workload.
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