Jump to content

ZO plus (the new kind)


disland
 Share

Recommended Posts

  • Baller

I have rev s with new plus. It is not for those who get on and off the the handle through the load process. If you are a upper body mover you probably will get pulled out of your body position. Bigger skiers that can maintain good load position it should be beneficial. It does come into the course a couple .10s faster then the other standard settings.

Just another 6 settings, If it fits wear it!

Link to comment
Share on other sites

  • Baller

fwiw -

ZERO OFF Versions

 

REV Q - Added the 9 settings – A1, A2, A3, B2, B3, C1, C2, C3

 

REV R – Added Slalom + WITH an additional 9 higher settings A1+, A2+, A3+, B2+, B3+, C1+, C2+, C3+ and increased gate entrance speed

 

REV S - Enhanced the existing SLALOM + setting with a firmer more responsive pull when “+” is used. Modified Master gains to - RS_Kp 4.0 / RS_Ki 2.5. Made gate entrance speed the same as “Slalom Normal” mode

Link to comment
Share on other sites

  • Baller

ZO is basically a PID controller (proportional-integral-derivative). The basic PID formula below:

d5azv437qofe.png

U is the 'output signal'; the value applied to the control actuator in the boat. For example to control the forward speed of the boat, U would be the throttle setting. The variable e is called the error, and it is the difference between the desired value and the actual value. For example, if the boat set speed is 55kph but moving actual of 56kph or 54kph the error would be -1/+1kph. The U value is simply a sum of three terms called the proportional, integral and differential terms. Each term has a positive constant K that must be manually tweaked for the controller to work as desired, multiplied by some function of the error.

 

The proportional term adjusts the control signal based on the magnitude of the error at present time. This means that the larger the error at any instant, the greater the control signal that is applied at that instant. If we are moving at 56kph but our goal is 55kph, the error would be -1, and the proportional term would subtract -1*Kp to the output signal, effectively decreasing the throttle. The slower we are moving relative to the goal of 55kph the higher the applied throttle, and the faster we are moving over 55kph the lower the applied throttle. Although this may seem to be enough to make the controller work, proportional tuning only would yield way too much speed delta; thus why the integral and differential terms are often times necessary.

 

The integral term adjusts the control signal proportionally to the magnitude of accumulated error over past times. The more error that has accumulated, the higher the control signal that is applied. Note that negative error can cancel positive error. In the boat speed example, if we have been moving at 30kph for 12 seconds, while the goal is 55kph, the accumulated error would be (55-30)*12=180, and we would add 180*Ki to the output signal, effectively increasing the throttle. The more time spent below goal, the more throttle will be applied. While the proportional term adjusts the output based on the present error, the integral term adjusts the output based on past errors. The goal of the integral term is to reduce the steady-state error to zero so we can reach the speed goal. The more time we spend with a positive error, the more throttle the integral term will apply, until we eventually get to our desired speed. The integral term will obtain the goal, but will probably overshoot it and induce oscillations.

 

The differential term is to dampen oscillations in the state; the goal of 55kph with minimal or no overshooting (or oscillations). The differential term adjusts the control signal proportionally to the rate of change of the error with respect to time, or how fast the error is changing. If the boat is moving at 53kph with a goal of 55kph, our error is 2. If we are accelerating such that we are gaining 1kph every second, the error is going down 1 every second, and the differential of the error with respect to time is -1. The PID would add -1.0*Kd to the output signal, reducing the throttle. The faster the boat approaches our goal of 55kph, the lower the throttle is going to be. This has the effect of slowing down the approach to the goal to avoid overshooting it.

 

While the proportional term adjusts the output based on the present error, and the integral term based on the past error, the differential term adjusts the output based on a prediction of future error. Knowing how fast the error is changing tells you something about what the error is going to be in a future instant.

 

It’s easy to see there can be a plethora of possible Kp/Ki/Kd parameters that might be “good” “better”, “best”.

 

@lpskier – this might be Norske.

 

This crap matters to the engineers, of the 18 choices, one of them will be good enough; I just wanna ski more!

 

Link to comment
Share on other sites

So....@Glorsen, yes, I'm dazzled by the sheer weight and volume of the text above. But a response that included an answer to the questions asked would be even more dazzling: What does the "+" setting in Rev S do differently that the "+" setting in Rev R. We understand that the Rev S + gate speed as been reduced to be the same as "slalom normal" mode -- so skiers will not enter the course at an unfamiliar/faster speed generated with the Rev R + setting. But please explain "Modified Master gains to - RS_Kp 4.0 / RS_Ki 2.5".

 

You've defined and provided Rev S values for Kp and Ki above -- but you don't provide the Rev R values or explain how the Rev S modification affects engine rpm and/or boat speed as compared to Rev R.

 

For what its worth, I can explain what I "feel" when using Rev S "+": The boat is always "right there". I dont feel it gassing me at highest loading into the center line. And I dont feel it backing off rpms as my resistance to the boat decreases. This seems odd because the boat driver hears very quick and aggressive changes to engine rpm while I feel just a constant/consistent - pull. This is great when I'm strong, smooth and controlled. It translates to a great pull. But any mistakes resulting in to much tip grab or tail slide seem to be a lot more difficult to fight through. The boat wins. Anyway, all kidding aside, if you have a explanation of the difference between Rev R + and Rev S +, I'd really appreciate it.

 

I know Horton and others have taken a crack at explaining the modification in a different thread.

Link to comment
Share on other sites

@Gloersen - are you suggesting that the A/B/C/1/2/3/+ would correspond to one of the K variables in your equation? Maybe the letter is Kp and number is Ki? If so, I may have reached peak nerd and that might be the best description I have read regarding how the letters/numbers work.
Link to comment
Share on other sites

  • Baller

Even though I don't ski in tournaments anymore, I like to have a decent boat for friends I ski with that do.

 

Just FYI:

 

Rev S needs the new Puck in order to work, so if you are like me, running dual old Pucks on a 2007SN with Rev R, you need to change to the new Puck and the upgrade.

The new 3-Event ZO Puck and harness is $450 and the S Upgrade is $50.

Link to comment
Share on other sites

  • Baller
If I'm reading the segment times correctly, Jillian gets smoked the first half of the course using + and gets a bit slower ride the last half. Is that an advantage?? It may be if she got in trouble the first half and needs a little slower second half to run the pass. Of course, perhaps she got in trouble in the first half because she was getting smoked. All segment times are in tolerance using + and not using +. End course times are identical - both a little hot. I wonder if Jillian is 100 lbs. or lighter. Based purely on segment times, it would appear to me that Jillian is better off not using +. Or is my thinking incorrect? Which does Jillian prefer? Obviously, both pulls are legal.
Link to comment
Share on other sites

  • Baller

Initially I too drew the same conclusion, but Jody indicated this screen shot was coming into the course. The times may have been on the previous pass?

When I use +, I get a 7:14 2 ball time and a 16:95 end. On no plus, get a 7:15 2 ball with a 16:95.

Link to comment
Share on other sites

  • Baller

Nope base line no skier and mark hit it on the head times are previous run times.

Just goes to show that there are different ways of approaching the course.

Like I said in a previous post if you are a bigger skier that can maintain a good strong position behind the boat this plus setting may work with out getting ripped out by 450 hp at the gate! Of course dont get behind!

Link to comment
Share on other sites

  • Baller

There can be nuances with ZO and gate entry speeds, turn islands with curvilinear approaches, throttle application, setup distances, etc.

This video verifies what the ZO engineers deployed with Rev S; that the entry gate speed is set to 0.8% above baseline both for the “normal” and the “+” modes (as opposed to Rev R when “+” came in 1.6% above baseline). So basically gate entry speed with a 34.2 setting is ~34.45 for all settings (“normal”/”+”). 6 different settings x 2 shown.

Too much glare to see the display, but the digital readout is more accurate. It’s real-time over html via a NMEA2k (J1939 compatible) gateway tapped directly into the CAN. The pylon video is direct HDMI (no stream/no latency). The overlay recording is simultaneous real-time using OBS.

Link to comment
Share on other sites

  • Baller

Ok, I'm confused. The posts by @Jody_Seal and @Gloersen seem to directly conflict.

I know Rev R + came in significantly faster than 'normal' and thought Rev S still came in slightly faster than 'normal', but not as fast as Rev R.

 

The advantage of coming in slightly fast is that the speed control won't have to apply as much throttle to keep the speed from dropping way down, i.e. the stronger/heavier skier won't get hammered as much as the boat coming in only a tenth or 2 hot.

 

FWIW, I use C1+, but its not quite as good as plain ole trick mode. I may have to try this experiment once the water warms up.

If it was easy, they would call it Wakeboarding

Link to comment
Share on other sites

  • Baller

@Bruce_Butterfield - ZO engineering tech replied to my inquiry a while back with:

REV S - Enhanced the existing SLALOM + setting with a firmer more responsive pull when “+” is used. Modified Master gains to - RS_Kp 4.0 / RS_Ki 2.5. Made gate entrance speed the same as “Slalom Normal” mode

 

It was implied that the Kp/Ki Master gains were tweaked upward (I don't have the "normal" Kp/Ki gains to compare). If the above are the only Rev S "changes", it also implies that the Kd gains and clipping values for Rev S in "+" mode are the same as in Rev R "+" (greater Kd gains and clipping value spread). Reasonable to assume the greater Kp/Ki will create greater throttle control in the heavier skier's handle, so gate entry speed will be more influenced by skier technique, also permitting using (unloaded) gate entry speeds the same as "normal" (0.8% above baseline). Unfortunately I'm not skiing well enough right now to explore this stuff.

 

7loxe43py2e9.png

 

 

Link to comment
Share on other sites

  • Baller
@ALPJr - I started slalom and jump behind a '74 Glastron tri-hull open bow with a Chrysler 130 hp outboard, so I can relate. The Santa Clara County Water Ski Club begrudgingly let my family join in 1976 with that boat (they really wanted us to have a Nautique or MC) and the most amazing thing to me is that my dad, with zero course or jump driving experience, and driving that dang boat, pulled me up through 36 mph long line and to jumps of about 120 feet. We didn't know any better at the time. Ignorance really is bliss sometimes.
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...