Implementation of analog circuit PWM

This picture shows a PWM generation circuit that uses a linear potentiometer (or linear Hall element) on a game controller or model aircraft joystick to control two chassis drive motors. J1 is the socket of the handle, 123 and 456 are the potentiometers in the x and y directions respectively. U1B provides half supply voltage and U1A is the voltage follower. The x and y components are synthesized into voltage signals that control the speed of the two motors of the left and right wheels. In use, let L=(x+1)y/(x+1.4), R=(x-1)y/(x-0.6), and it has good results after testing (the numbers are just units, not voltage values) . The voltage is converted into the corresponding PWM signal through the Schmitt oscillator composed of U1C and U1D, which is used to control the power drive circuit. Taking U1D as an example, R1 and R2 form a Schmitt circuit with hysteresis. The upper and lower thresholds are affected by the input voltage. C1 and R3 form a delay loop, so that the pulse width of the oscillation is controlled by the input voltage. Q1 and Q2 are transistors that form an inverter and provide differential control signals. For the specific oscillation process, please refer to the analysis of the 555 oscillator in the digital circuit textbook.