How measure speed?

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How measure speed?

Postby shahrul » Mon May 18, 2009 10:15 am

I want to measure speed of moving object. I think many ways can be do.
Encoder, accelerometer, GPS or other. I want to know how the concept and the performance?
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Re: How measure speed?

Postby sich » Mon May 18, 2009 10:47 pm

It depends on the application you wish to apply the speed measurement. Usually encoder is for wheeled mobile robot and linked system like robot arm. Accelerometer as its name suggests, it measures the acceleration. Normally, you can get X, Y and/or Z-axes measurement in a single chip. It's used in system which needs to capture impact to execute some actions. For example the air beg system in modern car, humanoid balancing control and so on. While for GPS, if not mistaken the best resolution we can get as consumer is around a few meters. So It's good for navigation which doesn't need very high accuracy, but requires wide coverage area.
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Re: How measure speed?

Postby shahrul » Tue May 19, 2009 9:37 am

Let say, I want to develop digital speedometer for my motorcycle.

sich WROTE:Usually encoder is for wheeled mobile robot and linked system like robot arm.
This way need to put encoder on the tyre and need tyre size calibration.

sich WROTE:Accelerometer as its name suggests, it measures the acceleration. Normally, you can get X, Y and/or Z-axes measurement in a single chip. It's used in system which needs to capture impact to execute some actions. For example the air beg system in modern car, humanoid balancing control and so on.
The accelerometer measure accelaration, so to get speed/velocity I need to integrate that measurement in term of time. How accurate this?

sich WROTE:While for GPS, if not mistaken the best resolution we can get as consumer is around a few meters. So It's good for navigation which doesn't need very high accuracy, but requires wide coverage area.
GPS then, I think higher cost from the other way. Because of very far satellite distance, maybe the reading have an error a few meters right?
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Re: How measure speed?

Postby AMD » Wed May 20, 2009 3:53 am

hmm.. u said digital speedo meter for ur motorcycle...

well, for ur seensor, u can use a gear tooth sensor (magnetic pickup)..
this kind of sensor also being use for ABS devices on car AFAIK...
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Re: How measure speed?

Postby shahrul » Wed May 20, 2009 9:54 am

AMD WROTE:well, for ur seensor, u can use a gear tooth sensor (magnetic pickup)..
this kind of sensor also being use for ABS devices on car AFAIK...

It's sound interesting. That way is measuring tooth gear by magnetic! Where can I place that sensor? At the spoket?
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Re: How measure speed?

Postby AMD » Wed May 20, 2009 12:27 pm

yes... u can use the sprocket if u want...
and when placing the sensor, u have to ensure that
it as rigid as possible with sensing gap in spec...
MOVE FOR FREEDOM
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