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| import numpy as np | |
| def CalcChassisVelocityFromWheels(wheel_vel): | |
| """ | |
| Compute chassis body-frame velocity from three wheel angular velocities for a | |
| three-wheel omnidirectional chassis. | |
| Input | |
| ----- | |
| wheel_vel : np.ndarray, shape (..., 3), float | |
| Wheel angular velocity array (unit: rad/s). | |
| Order: [wheel_front_left_velocity, wheel_front_right_velocity, wheel_rear_velocity] | |
| Output | |
| ------ | |
| chassis_vel : np.ndarray, shape (..., 3), float | |
| Chassis body‑frame velocity vector [v_x, v_y, omega_z]. | |
| - v_x: body‑frame linear velocity along x axis (m/s) | |
| - v_y: body‑frame linear velocity along y axis (m/s) | |
| - omega_z: body‑frame angular velocity around z axis (rad/s) | |
| Output shape matches input batch dimensions. | |
| Constants | |
| --------- | |
| SQRT3_OVER_2 : float | |
| √3 / 2 ≈ 0.8660254037844386, geometric coefficient for wheel layout. | |
| RWHEEL : float | |
| Wheel radius, unit: meter. | |
| RCHASSIS : float | |
| Distance from chassis center to each wheel mounting point, unit: meter. | |
| """ | |
| SQRT3_OVER_2 = 0.8660254037844386 | |
| RWHEEL = 0.101555 | |
| RCHASSIS = 0.32485 | |
| # Initialize output array with same batch dimensions as input | |
| chassis_vel = np.zeros_like(wheel_vel) | |
| # Body‑frame v_x (m/s) | |
| chassis_vel[..., 0] = ( | |
| (wheel_vel[..., 0] - wheel_vel[..., 1]) * RWHEEL / (2.0 * SQRT3_OVER_2) | |
| ) | |
| # Body‑frame v_y (m/s) | |
| chassis_vel[..., 1] = ( | |
| (2.0 * wheel_vel[..., 2] - wheel_vel[..., 0] - wheel_vel[..., 1]) * RWHEEL / 3.0 | |
| ) | |
| # Body‑frame angular velocity omega_z (rad/s) | |
| chassis_vel[..., 2] = ( | |
| -(wheel_vel[..., 0] + wheel_vel[..., 1] + wheel_vel[..., 2]) | |
| * RWHEEL | |
| / (3.0 * RCHASSIS) | |
| ) | |
| return chassis_vel | |