将两个UIAccelerationValue相加？

Question

我不确定这是不是一个愚蠢的问题，所以请在这里容忍我。不管怎样，我有两个UIAccelerationValue's。当我逐个NSLog他们的结果时，我得到的值分别如下：

1. Value: -0.016186

2. Value2: -0.033460

但是，当我将两个UIAccelerationValue's相加或相减时，得到的值如下所示：

Value: -571.142049
Value: -1085.174017
Value: -2061.834754
Value: -3917.490156
Value: -7443.235420
Value: -14142.151420

正如你所看到的，这些值一直在以指数级增长。

无论如何，我怎么能简单地将两个UIAccelerationValues相加或相减，而没有现在得到的结果呢？

Answer 1

我认为你是在存储加/减的结果，并且一遍又一遍地加/减，因此增加了很大的值。

UIAccelerationValue只是一个double (参见UIAccelerome.h)：

typedef double UIAccelerationValue;

通过以下示例，您将获得预期的输出：

UIAccelerationValue xOne = -0.016186;
UIAccelerationValue xTwo = -0.033460;

NSLog(@"%f", xOne + xTwo); // prints out -0.049646
NSLog(@"%f", xOne - xTwo); // prints out 0.017274

Answer 2

我不是UIAcceleration方面的专家，但这里有一个来自示例代码的示例。希望能有所帮助。

#define kAccelerometerFrequency        50.0 //Hz
#define kFilteringFactor 0.1


UIAccelerationValue gravX;
UIAccelerationValue gravY;
UIAccelerationValue gravZ;
gravX = (acceleration.x * kFilteringFactor) + (gravX * (1.0 - kFilteringFactor));
gravY = (acceleration.y * kFilteringFactor) + (gravY * (1.0 - kFilteringFactor));
gravZ = (acceleration.z * kFilteringFactor) + (gravZ * (1.0 - kFilteringFactor));

UIAccelerationValue accelX = acceleration.x - ( (acceleration.x * kFilteringFactor) + (gravX * (1.0 - kFilteringFactor)) );

UIAccelerationValue accelY = acceleration.y - ( (acceleration.y * kFilteringFactor) + (gravY * (1.0 - kFilteringFactor)) );
UIAccelerationValue accelZ = acceleration.z - ( (acceleration.z * kFilteringFactor) + (gravZ * (1.0 - kFilteringFactor)) );
accelX *= 9.81f;
accelY *= 9.81f;
accelZ *= 9.81f;
accelX = [self tendToZero:accelX];
accelY = [self tendToZero:accelY];
accelZ = [self tendToZero:accelZ];

UIAccelerationValue vector = sqrt(pow(accelX,2)+pow(accelY,2)+pow(accelZ, 2));
UIAccelerationValue acce = vector - prevVelocity;
UIAccelerationValue velocity = (((acce - prevAcce)/2) * (1/kAccelerometerFrequency)) + prevVelocity;

NSLog(@"X %g Y %g Z %g, Vector %g, Velocity %g",accelX,accelY,accelZ,vector,velocity);