So you want to use an accelerometer? I admit that would be sleeker looking and easier to put on to your arm, but it's going to be a lot harder to get it to track well than by using potentiometers rigged to move with the joints of the arm. For one thing accelerometers only track acceleration in straight lines. You would have to use several of them and some extreemly clever coding to make this work. Say you get the sensor working and it gives your program a sizeable accelleration in the x direction from a sensor on the persons hand. Did the person rotate their wrist rapidly, turn their hand up and move it up, or did they swing their arm out? Theres no way to tell for sure. Using multiple sensors you can interpret motion better, if theres one on each side of the hand, and they accelerate in opposite directions, the hand turned, if they accelerate in the same direction, it moved. But the software to interperet that kind of motion well is extreemly sophisticated, even if you can write it, there are few chips that could handle it and you would need several sensors. Try just making a program which points an arrow in the direction you move the accelerometer as you move it around, and you'll see what I mean.

 

thanks again Triode for your help ....
so i have to work with several senors :\

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show me and i will do it

 

That depends on what kind of detail you want. Have you ever used a wii remote? It can kind of tell what you're doing, like most of the time it moves in basically the same direction you do, and it can usually recognize "gestures" (these are not hand gestures but broad movements like swinging an arm in an arc), but not within a precise range. That's what you can do with 1 accelerometer.

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-Paul

 

no i didnt use this remote ...how can i get it and if there is any other choice

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Oh, I wasn't reccomending using a wii remote, its a game controller, I just thought that would be a good example of a one excellerometer system if you had seen one. Though it actually uses a bit more than just the excellerometer, it has an IR sensor array that references a pair of IR LEDs which are about a foot apart, by comparing the distance it sees between them, their location, and their angle relative to eachother. It can detect its relative location to them, and its roll. But you probably dont want to work with stuff that advanced.
Anyway, what you do want to use still depends on the amound of precision you need, and how simple and cheap it has to be. For high precision I would still recomend mechanical sensors (potentiometers) rigged to a thing that is worn on the person's arm. Besides precision, this offeres the advantage that its output will be compatible with a radio control set without any conversion, though you might need to add something simple for calibration.
But if you want something mechanically simple and high tech looking, although it will only roughly follow the motions of the person controlling it, the accelerometer may work. But for that you will need to program a microcontroller to interperet the accelerometer, and setup some kind of wireless transmission method, as well as a reciever that could interperet the signals and put out the apropriate PWM signal for the servos. This could be simplified using microcontrollers with built in RF units, but it would still be a tall order. You would need to understand pic programming well enough to do multitasked pwm to run the servos, some fairly intuitive AI to interperet the accelerometer, A/D conversion (depending on the output of your sensor, but this is an easy part), and set up the encoding, transmission, reception and decoding of the data.
Personally I'd take the first approach, mechanically more complicated but electronically simple, but then I'm a Mechanical Engineering Student, not a Software or Electrical Engineer.

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-Paul