自平衡两轮车辆的水平加速度测量？

Question

it's now the standard practices to fuse the measurements from accelerometers and gyro through Kalman filter, for applications like self-balancing 2-wheel carts: for example: http://www.mouser.com/applications/sensor_solutions_mems/

accelerometer gives a reading of the tilt angle through arctan(a_x/a_y). it's very confusing to use the term "acceleration" here, since what it really means is the projection of gravity along the devices axis (though I understand that , physically, gravity is really just acceleration ).

here is the big problem: when the cart is trying to move, the motor drives the cart and creates a non-trivial acceleration in horizontal direction, this would make the a_x no longer a just projection of gravity along the device x-axis. in fact it would make the measured tilt angle appear larger. how is this handled? I guess given the maturity of Segway, there must be some existing ways to handle it. anybody has some pointers?

thanks Yang

Answer 1

You are absolutely right. You can estimate pitch and roll angles using projection of gravity vector. You can obtain gravity vector by utilizing motionless accelerometer, but if accelerometer moves, then it measures gravity + linear component of acceleration and the main problem here is to sequester gravity component from linear accelerations. The best way to do it is to pass the accelerometer signal through Low-Pass filter. Please refer to Low-Pass Filter: The Basics or Android Accelerometer: Low-Pass Filter Estimated Linear Acceleration to learn more about Low-Pass filter.

Sensor fusion algorithm should be interesting for you as well.