Helicopters

gatekeeper motor controllers support a constant rpm mode for use on helicopters rpm mode will attempt to maintain the commanded rpm regardless of load on the drive train configuring unit for rpm mode helicopter use the following settings are required to be accurately set in order to use the motor controller in a typical helicopter application which limits the rpm of the motor to a desired range or a single fixed rpm this also allows for a soft start ramp of the motor to reduce stress on any mechanical components in the drive train no additional hardware is needed for this functionality drive mode this setting controls how the motor controller responds to different throttle commands, for helicopters it is recommended to set this to rpm mode in rpm mode the unit will map 1% to 100% throttle to a fixed rpm value and attempt to maintain that rpm regardless of load on the drive train see the drive mode documentation for more details motor pole pairs this setting tells the unit how many pole pairs are on the motor pole pair count is determined by how many permanent magnets are on the motor and then dividing this value by two this value is crucial for rpm related functionality as it is what the unit uses to convert the electrical rpm (erpm) to mechanical rpm rpm mode minimum (rpm) this is the minimum mechanical rpm the motor controller will spin the motor when a throttle above 0% is commanded when operating in rpm mode and the “soft start ramp time” has elapsed rpm mode maximum (rpm) this is the maximum mechanical rpm the motor controller will spin the motor, this rpm will be targeted when the commanded throttle is 100% and the “soft start ramp time” has elapsed this can be set to be the same value as the “rpm mode minimum” to spin the motor at a fixed rpm when this is set to greater than the “rpm mode minimum” the throttle input linearly scale the target rpm output between the minimum and maximum rpm values rpm mode soft start ramp time (seconds) this is the time spent linearly ramping the motor to the commanded rotational speed higher values for this setting will cause a slower ramp and are intended for drive trains with a higher moment of inertia the default value for this is 10 seconds, meaning once throttle is applied the motor will reach the commanded rpm in 10 seconds once this time has elapsed throttle commands will cause a ramp to the target rpm with configured ramp up and ramp down rates configuring rpm mode tuning parameters the following two parameters control the pi control loop which controls the rpm when using rpm mode we recommend using the default values and testing if tuning of the rpm control is needed then the following two parameters can be changed similar to any other pi controller below we discuss how the parameters affect the system and how to change them to tune rpm mode for your application rpm mode proportional control this parameter refers to the "proportional" (p) component of the rpm mode pi control system purpose it adjusts the output of the esc (e g , power to the motor) in proportion to the difference between the target rpm (setpoint) and the actual rpm measured from the motor how it works if the motor is spinning slower than the desired rpm, the proportional control increases the power output to speed it up conversely, if the rpm is too high, it reduces power the adjustment is immediate and directly proportional to the size of the error effect a higher proportional gain results in a stronger and faster response to correct the rpm error, but if set too high, it can lead to oscillations or instability (overshooting the target rpm) if set too low, the response may be sluggish, and the motor might not reach the target rpm accurately tuning consideration this is typically the first parameter tuned in a pid system, as it provides the primary correction mechanism rpm mode integral control this parameter refers to the "integral" (i) component of the rpm mode pi control system purpose it addresses the cumulative error over time that the proportional control alone cannot fully eliminate it ensures that the motor eventually settles precisely at the target rpm, even if there are persistent external factors (like load changes or friction) causing a steady state error how it works the integral control calculates the sum (or integral) of the rpm error over time if the motor consistently runs below the target rpm, the integral term gradually increases the esc’s output to compensate, and vice versa if it’s above the target this eliminates residual offset that proportional control might leave behind effect a higher integral gain can correct steady state errors more quickly, but if set too high, it can cause overshoot or ringing (oscillations around the target rpm) if too low, it may take too long to eliminate the error, or the rpm might never fully stabilize at the setpoint tuning consideration this is often tuned after the proportional term, ensuring it complements the proportional response without introducing instability