Post by thread:[PIC]: Rate-Sensor use for motion-control

Greetings All.... Could use some input on a formula or any other experience....... Using a GyroChip-II "Rate-Sensor" and performing an A-D (12-bit). The data is combined with another 16-bit source (joystick-output) to produce a command position value. The value is then sent over to a PMD (Performance Motion Devices) to operate the motor. The joystick serves to position the axis, while the Rate- Sensor acts to stabilize the axis (vibration, etc.) I'm having a difficult time determining what calculation I could use (within a PIC16F873) .......in assembly lang. Any algorithms out there for such a task ? Thanks! Steve Kelley __________________________________________________ PROTOBYTE INC. http://www.protobyte.com 14208 Zachary Dr. Liberty, MO 64068 Email: spam_OUTinfoTakeThisOuTprotobyte.com Phone: (816)-792-0235 Fax : (816)-792-0595 ___________________________________________________ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

>> Using a GyroChip-II "Rate-Sensor" and performing an A-D (12-bit). The data is combined with another 16-bit source (joystick-output) to produce a command position value. The value is then sent over to a PMD (Performance Motion Devices) to operate the motor. The joystick serves to position the axis, while the Rate- Sensor acts to stabilize the axis (vibration, etc.) I'm having a difficult time determining what calculation I could use (within a PIC16F873) .......in assembly lang. Any algorithms out there for such a task ? << One of my current projects envolves dealing with real time gyro and accellerometer data on a 16F877. I do various analysis and filtering on the data both in integer and floating point. Beyond that I don't know what to tell you because I don't understand your question. Perhaps you could be more specific. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, olinKILLspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

Olin Lathrop wrote: {Quote hidden}> > >> > Using a GyroChip-II "Rate-Sensor" and performing > an A-D (12-bit). The data is combined with another > 16-bit source (joystick-output) to produce a command > position value. The value is then sent over to a PMD > (Performance Motion Devices) to operate the motor. > > The joystick serves to position the axis, while the Rate- > Sensor acts to stabilize the axis (vibration, etc.) > > I'm having a difficult time determining what calculation > I could use (within a PIC16F873) .......in assembly lang. > > Any algorithms out there for such a task ? > << > > One of my current projects envolves dealing with real time gyro and > accellerometer data on a 16F877. I do various analysis and filtering on the > data both in integer and floating point. Beyond that I don't know what to > tell you because I don't understand your question. Perhaps you could be > more specific. It sounds like a controls question. Although that depends on why the PIC is processing the inputs, which isn't very clear. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Brandon....... You're right, I left out alot of details, because much more is happening with the PIC's, that's not related to the data-integration for producing the position error. The PIC utilizing the equation (or in need of one) is actually working within a Master/Slave topology. It happens to be the Slave and handles USART & SPI data, as well as performing the integration. The joystick data is received at 19.2K baud over an async.-serial-port, using a 4-byte packet. The packet breakout is not important here, but it does contain 16-bits of "position-information" that is used to operate "one" axis through a PMD-Chipset..... which then drives (via Sign-Mag) an LMD18200 H-bridge (as a Servo-motor). The rate-sensor is located remotely and uses a GyroChip-II Sensor, conditioned via 3rd, order Butterworth (100hz. cutoff) and then passes to a MAX-187 12-bit A-D. We sample at 6250hz. and the Slave gathers SPI data at 1.2mbs Both the Rate-Sensor data and the joystick data must be integrated to provide a single "position error". With the outcome being "two" independant error sources, which when integrated have an equal effect on the Servo's position error. A scaling of the two errors is necessary too. Hope this shines more light.........it's about all that I can disclose. My "main" problem is lacking the ability to develop assembly routines that perform much more than the "basic-four", within a narrow time-frame of ~ 10 to 15 uSEC. while operating at 20mhz. clock. Also, I'm one of those that happens to be "C-challenged", meaning ....... can't easily read/write it. Thus, I work with assembly only. Of course, when my clone is ready, I'll be sending him to school again......full-time. So, now we come to the "nutshell"........ ********************************************************************** "I'm looking for assembly based algorithms, that can provide integration functions and exceed the level of only basic math". ********************************************************************** Regards, Steve Kelley P.S. Where can I pick-up some singing potatoes ? They sound like easy "pets" to maintain 8^) {Original Message removed}

I would recommend giving yourself more time. With your anti-aliasing filter as it is, you have 72dB attenuation at 1600 Hz, which means that a 3200 Hz sample rate will guarantee that all aliases are smaller than one least-significant bit. One more op-amp can get you to a 6th-order filter, and then you can get your sample rate down to 800 Hz. All this is assuming that your 100-Hz cutoff actually implies that you are only interested in data below 100 Hz, which is probably pretty reasonable for a gyro application. I would heartily recommend downloading the FilterLab program from the Microchip website. When doing signal processing with a relatively arithmetically-challenged processor like a PIC, step 1 must be to do a little work on the front end to get the sample rate as low as possible. > {Original Message removed}