Documentation Index
Fetch the complete documentation index at: https://mintlify.com/MuShibo/Micro-Wheeled_leg-Robot/llms.txt
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The firmware uses nine PIDController instances and three LowPassFilter instances, all provided by SimpleFOC. They form a cascade: the outer pitch/yaw/roll loops generate torque setpoints, a dead-band compensator handles the non-linear motor region near zero, and an adaptive integrator slowly trims the balance zero-point. Every controller is registered with the SimpleFOC Commander so its parameters can be adjusted over the Serial monitor at 115 200 baud without reflashing.
PID Controllers
All PIDController instances are declared with {.P, .I, .D, .ramp, .limit} initialiser syntax. The ramp field limits the rate of change of the output per second; all controllers use 100000 (effectively unlimited) to preserve control bandwidth.
| Commander | Variable | P | I | D | Ramp | Limit | Role |
|---|
A | pid_angle | 1.0 | 0 | 0 | 100 000 | 8 | Pitch angle error → balance torque |
B | pid_gyro | 0.06 | 0 | 0 | 100 000 | 8 | Pitch rate (gyro Y) → balance torque |
C | pid_distance | 0.5 | 0 | 0 | 100 000 | 8 | Wheel displacement error → balance torque |
D | pid_speed | 0.7* | 0 | 0 | 100 000 | 8 | Wheel speed error → balance torque (*adaptive) |
E | pid_yaw_angle | 1.0 | 0 | 0 | 100 000 | 8 | Accumulated yaw angle error → differential torque |
F | pid_yaw_gyro | 0.04 | 0 | 0 | 100 000 | 8 | Yaw rate (gyro Z) → differential torque |
H | pid_lqr_u | 1.0 | 15 | 0 | 100 000 | 8 | Dead-band non-linearity compensation (PI) |
I | pid_zeropoint | 0.002 | 0 | 0 | 100 000 | 4 | Adaptive balance zero-point integrator |
K | pid_roll_angle | 8.0 | 0 | 0 | 100 000 | 450 | Roll angle error → leg servo differential |
pid_lqr_u is the only controller with a non-zero integral term (I = 15). It only activates inside the dead-band (|LQR_u| < 5, joystick idle, |distance_control| < 4, not jumping). Its integrator is explicitly cleared (pid_lqr_u.error_prev = 0) whenever the dead-band condition is not met, preventing wind-up.
Low-Pass Filters
SimpleFOC LowPassFilter instances are first-order IIR filters with time constant Tf (seconds). Smaller Tf = faster response but less smoothing.
| Commander | Variable | Tf (s) | Input Signal |
|---|
G | lpf_joyy | 0.2 | Joystick Y (wrobot.joyy) — smooths speed commands to the LQR speed term |
J | lpf_zeropoint | 0.1 | distance_control — filters the signal driving the adaptive zero-point integrator |
L | lpf_roll | 0.3 | Roll angle (mpu6050.getAngleX() + 2.0) — smooths roll compensation before the servo PID |
Motor Velocity PID
The SimpleFOC inner velocity loop for each wheel motor is configured directly in setup() and is not accessible via the Commander interface. These values act as an anti-cogging inner loop within the voltage torque controller.
motor1.PID_velocity.P = 0.05;
motor1.PID_velocity.I = 1.0;
motor1.PID_velocity.D = 0;
motor2.PID_velocity.P = 0.05;
motor2.PID_velocity.I = 1.0;
motor2.PID_velocity.D = 0;
Adaptive pid_speed Gain
pid_speed.P is overwritten every loop iteration in lqr_balance_loop() based on the current leg height. The Commander-set value for channel D will be overridden at runtime.
Leg Height (wrobot.height) | pid_speed.P |
|---|
| < 50 | 0.7 |
| 50–63 | 0.6 |
| ≥ 64 | 0.5 |
Commander Syntax Reference
The Commander reads single-character channel identifiers from Serial (115 200 baud). Each channel maps to a registered PID or LPF instance. The syntax follows the SimpleFOC Commander convention:
<Channel><Field><Value>
Fields:
P = proportional gain
I = integral gain
D = derivative gain
F = low-pass filter time constant (Tf)
R = output ramp limit
L = output limit
Examples:
AP1.5 → pid_angle.P = 1.5
BP0.08 → pid_gyro.P = 0.08
HI20 → pid_lqr_u.I = 20
GF0.15 → lpf_joyy.Tf = 0.15
KL300 → pid_roll_angle.limit = 300
DP0.55 → pid_speed.P = 0.55 (overridden by adaptive logic each loop)
A) prints the current values of that controller to Serial.
Commander changes are volatile and are lost on reboot. When you find values that work well, copy them back into the corresponding PIDController or LowPassFilter initialisers in wl_pro_robot.ino before reflashing.
SimpleFOC Commander echoes the new parameter value back over Serial immediately after a write. Watch the Serial Monitor to confirm the value was parsed correctly — a malformed string (e.g. missing numeric digits) will leave the parameter unchanged and Commander will not print an acknowledgement.