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### Summary of my Problem:

1. **Setup: **
- a wheelchair with three motors.
- Two of the motors drive the rear wheels, which have a diameter of 680 mm, and these motors share the same controller and have a diameter of 83 mm.
- The third wheel is the front wheel, which has a diameter of 290 mm and is driven by a separate motor with its own controller.
- You want all three motors to work together to maintain the same speed, controlled by a single throttle.

2. **Problem: **
- The two rear motors are identical and work together with the same controller, meaning they naturally synchronize.
- The front wheel motor has a different controller and drives a wheel of a different size, which requires this controller to compensate for the difference in wheel size to ensure the front wheel moves at the same rotational speed as the rear wheels.

3. **Challenge: **
- The challenge is that the front motor needs to adjust its speed correctly relative to the rear wheels, even though the wheels it drives are of different sizes. All of this must be controlled by a single throttle. This requires the front motor's controller to either increase or decrease its output to match the speed of the rear wheels.

### Solution:
To solve this problem, you'll likely need an advanced controller that can account for the differences in wheel size and compensate accordingly. There are controllers available that can handle multiple motors with different specifications while still ensuring synchronized speed. Alternatively, you might consider using a central unit (like a microcontroller or PLC) that receives the signal from the throttle and then controls the individual motor controllers based on the required rotational speed for each wheel.

Finding the right solution can be challenging, so it might be helpful to consult an engineer or technician with experience in motor control systems for specific recommendations on hardware and software that can handle this type of situation.

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Let me know if you need any further adjustments!