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autopilot review
- Thread starter jimb522
- Start date
WBChristie
New member
Did you use the S1000 pump with it? I would like to build a ram myself to eliminate the above deck electric tiller drive. I would appreciate as much info as you are willing to share.
Thanks
Gary
WBChristie
New member
Just saw that you use a type 1 pump in a previous post. I'm curious if you used a PLC or something like that for the "brain"?
brianb
Olson 34 Driver
I used the S1000 pump driving a teleflex hydraulic cylinder. Pressure hoses are Teleflex purchased from a supplier off of ebay who customizes the length and has the tools to crimp the high pressure fittings (up to 1000lbs PSI). The hydraulic cylinder is made for outboard motor and stern drive application and is very seaworthy as it is made for direct exposure in the stern well of a power boat. As I said there is no reason to choose this pump. I choose it for cost and lack of clutch valve, which I did not want to power. The pump is a little nosier than a similar pump used in an NKE installation. The pump lasted me approx 9000 ocean miles until finally the motor brushes wore out. This happened several months back on the bay.
I have a small PVC tank for the hydro. fluid that I made from a section of PVC pipe. In the course of 5000 miles I added about 5 table spoons of fluid (or one west systems epoxy syringe full of Teleflex hydro. fluid).
Bleeding the system is easiest by using a pair of syringes to provide suction and compression. The vacuum helps get the air out.
The pump is either driven from my own AP electronics or an X5 controller. It ran night and day on the SHTP and the return trip. I did switch in the X5 tiller want occasionally while doing hydro. fluid refills or just wanting to hear a different note coming from my autopilot.
Does that help ?
Brian
I have a small PVC tank for the hydro. fluid that I made from a section of PVC pipe. In the course of 5000 miles I added about 5 table spoons of fluid (or one west systems epoxy syringe full of Teleflex hydro. fluid).
Bleeding the system is easiest by using a pair of syringes to provide suction and compression. The vacuum helps get the air out.
The pump is either driven from my own AP electronics or an X5 controller. It ran night and day on the SHTP and the return trip. I did switch in the X5 tiller want occasionally while doing hydro. fluid refills or just wanting to hear a different note coming from my autopilot.
Does that help ?
Brian
brianb
Olson 34 Driver
Oh, one other point, I spoke with the engineers at Teleflex. All their cylinders are made from the same materials. The only real difference is seal pressure ratings. They have two lines, one sounds more like a rugged ocean version. Actually not the case, the difference is the pressure rating. As I recall one line handles up to about 1200 psi, the other somewhat less. I only mention this because the lower cost unit is a very rugged design.
WBChristie
New member
Thanks for all of that Brian. I found this http://www.raymarine.com/view/?id=209 chart that shows which pump goes with which cylinder.. it could be useful for finding a cylinder for an existing pump or vice versa. It does not look like I will be saving any money over an electric linear drive, but it should be way more reliable. I do actually have a line on an S1000 pump, and might mate that with the new EV-100 brain and sensor..plus a i70 control head.
I just need to find a cylinder now, 10" stroke should be adequate. The low cost rugged Teleflex might be the way to go.
Brian, does the S1000 pump have a settable pressure relief valve? That thing will develop some serious force with a small cylinder.
I just need to find a cylinder now, 10" stroke should be adequate. The low cost rugged Teleflex might be the way to go.
Brian, does the S1000 pump have a settable pressure relief valve? That thing will develop some serious force with a small cylinder.
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brianb
Olson 34 Driver
Gary,
FYI: I found virtually new Teleflex cylinders on ebay from outboard shops that were taking them off boats who were changing to other engines. The near new cylinder I have has been flawless for years and many ocean miles. Seals don't leak. The cost was less than half of the new models.
FYI: I found virtually new Teleflex cylinders on ebay from outboard shops that were taking them off boats who were changing to other engines. The near new cylinder I have has been flawless for years and many ocean miles. Seals don't leak. The cost was less than half of the new models.
WBChristie
New member
Great! Thanks
pogen
Sailing canoe "Kūʻaupaʻa"
I just got this offer in my email, you can get a new Raymarine unit for free!
http://thechelseamagazinecompany.com/6NM-1S39K-2E76XVUPDC/cr.aspx
It's part of some contest from Yachts & Yachting Magazine, not a Nigerian autopilot scam.
When they talk about 9-axis, I guess they mean x, y, z, three angles, and three angular accellerations?? Or what? Or are some of those 'marketing' axes?
EDIT: I guess the best axes would be x'', y'', z'', thetax, thetay, thetaz, and thetax', thetay', thetaz'.
http://thechelseamagazinecompany.com/6NM-1S39K-2E76XVUPDC/cr.aspx
It's part of some contest from Yachts & Yachting Magazine, not a Nigerian autopilot scam.
When they talk about 9-axis, I guess they mean x, y, z, three angles, and three angular accellerations?? Or what? Or are some of those 'marketing' axes?
EDIT: I guess the best axes would be x'', y'', z'', thetax, thetay, thetaz, and thetax', thetay', thetaz'.
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pogen
Sailing canoe "Kūʻaupaʻa"
Hey you can get a 9-axis sensor on a single chip, it is made just a couple of miles from my house.
http://www.invensense.com/mems/gyro/mpu9150.html
http://www.invensense.com/mems/gyro/mpu9150.html
WBChristie
New member
The problem with the chip is how to interface it to an existing control. Very interesting though, thanks for sharing
pogen
Sailing canoe "Kūʻaupaʻa"
well maniacs like Brian are not afraid to roll their own!
I am kind of interested in getting a lower power ram for my system, it presently uses about 6A when the pump motor is on, and the solenoid draws 1A when engaged. I bought a very husky drive on the theory that a electric motor/gear drive would burn out under load. There must be something intermediate though.
WBChristie
New member
This is a great site that offers components that would make building your own doable: http://www.pololu.com/
They offer just about everything that a home brewer might need.. with the hydraulics being the exeption. It is very affordable stuff as well. Here is a video that shows a self balancing robot that uses cascaded PID control, very similar to what an autopilot would need: http://www.youtube.com/watch?feature=player_detailpage&v=DmoShkJclLI
They offer just about everything that a home brewer might need.. with the hydraulics being the exeption. It is very affordable stuff as well. Here is a video that shows a self balancing robot that uses cascaded PID control, very similar to what an autopilot would need: http://www.youtube.com/watch?feature=player_detailpage&v=DmoShkJclLI
brianb
Olson 34 Driver
My AP has 9 axis: XYZ for magnetic field, acceleration, and rate gyro's. No marketing axis or evil axis.
brianb
Olson 34 Driver
Here is a youtube of my AP design in action on Elise, an Express 27 on a gusty run through the slot, using all 9 axis of data to maintain course: https://www.youtube.com/watch?v=EWObyejTb3A
WBChristie
New member
That looks very good. Do you have any video of a quartering sea with a bit of wind? Are you going to sell these...?
pogen
Sailing canoe "Kūʻaupaʻa"
Brian, what kind of servo algorithm are you using? PID, or with some feedforward, or coupling of pitch to anticipated yaw?
For example, in a quartering sea, as a wave approaches the stern will rise first (pitch) and then heel a bit (roll), and then the boat will yaw, say consistently toward the side the wave is on. So a human will anticipate the yaw and counter steer as he feels the pitch change. I believe that this is what is going on with the better pilots like NKE. But most manufacturers don't talk about what they are doing or even how they are sensing. The Nexus compass has MEMS type accellerometers in it, but they don't say what kind, and it is not clear that all the data gets sent over the bus to their AP control head, which is a pretty old design.
Edit: I did a little poking around on the web, it looks like Kalman filters are the done thing for this kind of control problem. But how to build the matrices? Maybe that is what is going on inside my electronic compass, which can give a good heading output even when the boat is heeled over or pitching down a wave. I think the AP is pretty crude though, only a PI with a feedforward term for when you are way off.
If one had lots of time, you could log all with wind data, attitude data, BSP etc. on different points of sail and sea states with a good driver, and 'teach' the algorithm what to do that way. A neural net, I think.
For example, in a quartering sea, as a wave approaches the stern will rise first (pitch) and then heel a bit (roll), and then the boat will yaw, say consistently toward the side the wave is on. So a human will anticipate the yaw and counter steer as he feels the pitch change. I believe that this is what is going on with the better pilots like NKE. But most manufacturers don't talk about what they are doing or even how they are sensing. The Nexus compass has MEMS type accellerometers in it, but they don't say what kind, and it is not clear that all the data gets sent over the bus to their AP control head, which is a pretty old design.
Edit: I did a little poking around on the web, it looks like Kalman filters are the done thing for this kind of control problem. But how to build the matrices? Maybe that is what is going on inside my electronic compass, which can give a good heading output even when the boat is heeled over or pitching down a wave. I think the AP is pretty crude though, only a PI with a feedforward term for when you are way off.
If one had lots of time, you could log all with wind data, attitude data, BSP etc. on different points of sail and sea states with a good driver, and 'teach' the algorithm what to do that way. A neural net, I think.
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brianb
Olson 34 Driver
Hi Dave,
A few responses:
Compass: For mems sensors without a gimbled platform one has to maintain a computed artificial horizon in which to translate the magnetometer sensor 3 axis data. That is typically done with the accelerometers.
Filtering: Yes, I use Kalman filtering as do others. The accelerometers are particularly noisy and sensitive to high frequency vibration. For example motor vibration can create offsets in computed results. A fun thing to try, set your heading on a calm day under sail, then turn on the engine and see if an error is introduced. I have done this with a couple of commercial units and both had apparent errors introduced with engine noise, in the range of 5 degrees. I have seen both offsets and course wandering increase in noisy environments.
Sea State: Yes, I use all the sensors to compensate for boat attitude and sea state. I could discuss the guts of the algorithms over a beer somewhere. It kind of is the secret sauce of the design.
Data Capture: Yes, I capture all the sensor data and NMEA, when attached, on a PC. I have hours of recorded data. This has been used extensively to perfect results on the water. I attached an example plot that shows an RM X5 recovering from a step change in course (20 degrees). The motor pulse data can be ignored.
A few responses:
Compass: For mems sensors without a gimbled platform one has to maintain a computed artificial horizon in which to translate the magnetometer sensor 3 axis data. That is typically done with the accelerometers.
Filtering: Yes, I use Kalman filtering as do others. The accelerometers are particularly noisy and sensitive to high frequency vibration. For example motor vibration can create offsets in computed results. A fun thing to try, set your heading on a calm day under sail, then turn on the engine and see if an error is introduced. I have done this with a couple of commercial units and both had apparent errors introduced with engine noise, in the range of 5 degrees. I have seen both offsets and course wandering increase in noisy environments.
Sea State: Yes, I use all the sensors to compensate for boat attitude and sea state. I could discuss the guts of the algorithms over a beer somewhere. It kind of is the secret sauce of the design.
Data Capture: Yes, I capture all the sensor data and NMEA, when attached, on a PC. I have hours of recorded data. This has been used extensively to perfect results on the water. I attached an example plot that shows an RM X5 recovering from a step change in course (20 degrees). The motor pulse data can be ignored.