Using an arduino instead of/to control a quadcopter transmitter

I need to be able to change the rpm of my motors to specific constant values in order to take measurements for a school experiment. My transmitter joysticks aren't sensitive enough so i was wondering if its possible to control the quadcopter with an arduino, meaning i could input specific motor speed values. I dont need to be able to fly the quadcopter with my arduino, just input motor speed. I dont mind how its done, by attaching the arduino directly to the quadcopter or the receiver. Any help is appreciated. Thanks

It depends on the tx you have. Some are easier to hack because they use simple PPM and have a separate RF module. But some will be easier to read from the RX. More details please?

It's a 2.4ghz 4CH with 6 Axis Gyro

More specifically: What is the model? There are many 4-ch 6-axis quads. Please also include a picture of the transmitter.

Its an Aviax F2 from GPTOYS

You could theoretically take out the joysticks and use the Arduino with analogWrite and a resistor/capacitor network to output a constant value. What exactly are you trying to measure?

I'm measuring the relationship between propeller speed and thrust. I just need to be able to enter specific constant values for motor speed

Can you detach the motors from the controller? Then you can use an Arduino (with a motor driver module) to control the motors directly. For the propeller speed some feedback (encoder?) is required, which must be accessible to the Arduino as well. Details depend on whether such encoders are part of the quadcopter, or whether you have to add e.g. a light barrier to count the propeller turns.

Here’s the quadcopter flight controller. I’ve disconnected the lights and receiver module, only the motors are still connected.

Brushed motors. There is a MultiWii board that has built in 4 micro ESCs for brushed motors, and you could simply add transistors for extra current capability.