ios中陀螺仪CoreMotion的使用

以前在iphone中要得到加速度时，只能使用Accelerometer模块得到重力加速度分量，然后通过滤波得到加速度值。其实在ios中有一个陀螺仪模块，CoreMotion，使用更方便。

CoreMotion中主要有以下几个模块

初始化CoreMotion

[html]
view plaincopy

#import <CoreMotion/CoreMotion.h>

CMMotionManager *motionManager = [[CMMotionManager alloc]init];

1. Accelerometer 获取手机加速度数据

[html]
view plaincopy

CMAccelerometerData *newestAccel = motionManager.accelerometerData;
double accelerationX = newestAccel.acceleration.x;
double accelerationY = newestAccel.acceleration.y;
double accelerationZ = newestAccel.acceleration.z;

2. Gravity 获取手机的重力值在各个方向上的分量，根据这个就可以获得手机的空间位置，倾斜角度等

[html]
view plaincopy

double gravityX = motionManager.deviceMotion.gravity.x;
double gravityY = motionManager.deviceMotion.gravity.y;
double gravityZ = motionManager.deviceMotion.gravity.z;

获取手机的倾斜角度：

[html]
view plaincopy

double zTheta = atan2(gravityZ,sqrtf(gravityX*gravityX+gravityY*gravityY))/M_PI*180.0;

double xyTheta = atan2(gravityX,gravityY)/M_PI*180.0;

zTheta是手机与水平面的夹角， xyTheta是手机绕自身旋转的角度

3. DeviceMotion 获取陀螺仪的数据 包括角速度，空间位置等

旋转角速度：

[html]
view plaincopy

CMRotationRate rotationRate = motionManager.deviceMotion.rotationRate;
double rotationX = rotationRate.x;
double rotationY = rotationRate.y;
double rotationZ = rotationRate.z;

空间位置的欧拉角（通过欧拉角可以算得手机两个时刻之间的夹角，比用角速度计算精确地多）

[html]
view plaincopy

double roll = motionManager.deviceMotion.attitude.roll;
double pitch = motionManager.deviceMotion.attitude.pitch;
double yaw = motionManager.deviceMotion.attitude.yaw;

空间位置的四元数（与欧拉角类似，但解决了万向结死锁问题）

[html]
view plaincopy

double w = motionManager.deviceMotion.attitude.quaternion.w;
double wx = motionManager.deviceMotion.attitude.quaternion.x;
double wy = motionManager.deviceMotion.attitude.quaternion.y;
double wz = motionManager.deviceMotion.attitude.quaternion.z;

通过陀螺仪模块可以实现模拟赛车，模拟射击等