Ninebot One Z : Z6-Z8-Z10

[Chriull]

1 hour ago, Mono said:

I am still trying to understand what you mean precisely by "modulate".

"modulate" was introduced by you? Here I used/understood it as "controlling/setting" the value. The basic meaning is shaping a waveform - so by modulation (PWM) and then averaging one sets a voltage value.

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Is it not correct to say that the controller "passes" to the motor, depending on the duty cycle, either 0V or the battery voltage (which then undergoes the "step down")? In other words, there are only two voltages interlaced (from which we could compute a weighted average voltage)? Or in other words, the controller just turns the motor on and off repeatedly in very short periods of time?

Yes. Additionally the "motor" (mainly the coil inductance and a bit the inertia) performs the averaging of the two voltages with a certain duty cycle.

To be seen for example in the simulation posted here: 

http://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/?do=findComment&comment=104078

(legend is written in http://forum.electricunicycle.org/topic/7549-current-demand-versus-battery-voltage/?do=findComment&comment=103044, but in this post is unfortionately a fault in the schematics and hence also in the simulation....)

 

37 minutes ago, Tomek said:

... However, to the best of my knowledge, the controller can't "step down the voltage". It technically only opens and closes the transistors, but at very high speeds, which effectively can control the speed and torque of the motor. btw. PWM outputs of microcontrollers follow a similar principle. They don't "step down" the voltage, but by turning the output on and off at full voltage, you can create the effect as if the voltage was decreasing (e.g. a LED on your Arduino will fade down).

What you describe is the step down converter. By "opening and closing the transistors at very high speeds" one gets a stepped down voltage, since the coils of the motor are averaging this PWM impulses.

It is not only the effect - it's real. (In case of the led the eyes are performing the averaging, in case of the EUC the inductance of the coils of the motor (plus the whole system inertia). The PWM noise are the rest of the artifacts noticable of a not 100% perfect averaging)

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considering the toque equation, you can also say that if torque = power / speed then toque (in an instance of time) = current (flowing in that moment to the motor controller) x voltage (feeding the motor controller) / speed (of the motor). how current and voltage are specifically divided and fluctuating across the three motor phases, i.e. what happens between the controller and the motor is of no importance from this perspective IMO. Of course, due to heat losses, the power consumption of the motor will be a bit lower than the power consumption of motor+controller. 

Yes - the real dynamic simulation would be too complicated and overdone for our considerations here.

The "static" model with U_back_emf = speed * motor_constant and torque = i_current * motor_constant is sufficient.

 

One could also look at this system from the "other side":

If one drives with the EUC at a certain speed and a certain torque is provided by the motor, this needs a certain motor current and generates a certain back EMF (according to the above equations).

So at the motor one has a voltage of Back EMF plus I_motor times Ohmic_coil_resistance. This motor voltage has to be lower than the battery voltage, so that the needed motor current can flow into the motor.

So this motor voltage is defined by the abovementioned circumstances, variable and lower as the battery voltage.

Since voltage differences cannot vanish magically somehow this difference between Battery and motor voltage has to be "handled".

To put some (variable) ohmic resistance into the path, so that the according voltage drop is happening is not possible - way too much power would have to be dissipated! Would be some kWs in nowaday EUCs.

The other possibility would be a step-down converter....

[Slaughthammer]

1 hour ago, Mono said:

Or in other words, the controller just turns the motor on and off repeatedly in very short periods of time?

Basically, yes. But it's not that easy, you see. The controller is feeding an alternating voltage to some coils, and the envelope curve of that alternating voltage is also an alternating voltage. The first one has a frequency of some 6 to 25kHz, depending on the manufacturer. The second one has a frequency of 0-500Hz, depending on the present speed. So what happens if you feed this to some coils? As a competent scientist you should be able to figure this one out. Hint: there are phase variances involved.

Edited August 16, 2017 by Slaughthammer

[Mono]

6 minutes ago, Chriull said:

"modulate" was introduced by you?

true, I believe I was referring to "the controller which "steps down" the battery voltage as needed" as "modulate voltage".

[jojo33]

"It's not heavy, it's lighter than a salad !"

  

[Mono]

3 minutes ago, jojo33 said:

"It's not heavy, it's lighter than a salad !"

More precisely, lighter than 25kg of salad.

[Roland]

The road is long
With many a winding turn
That leads us to who knows where
Who knows when
But I'm strong
Strong enough to carry  (it  ) 

(It) ain't heavy, ´(It)'s my EEE UUU CCC 

...  

[Lukasz]

2 hours ago, jojo33 said:

"It's not heavy, it's lighter than a salad !"

  

More pictures please!  Any other more detailed news about the weight?  

ALSO if Ninebot people watch this thread ( I am sure they are )  PLEASE modify lower part of the pedals in such way that it is possible to kick the pedal to put it down as in this movie  

 

 

 

[Dancer]

If that rim is 18" than the pedals are at least 10" long. Nice.

Edited August 16, 2017 by Dancer

[Lukasz]

Also - can anybody from NINEBOT confirm if on IFA fairs in Berlin (1-6 of September) You are going to show the Z models?

I will be happy to visit Your stand in such case...

[LanghamP]

20 hours ago, LanghamP said:

 

That video is highly misleading because while a bicycle can coast an EUC pushes huge and sudden power pulses to keep you balanced. I'm convinced that a tire/wheel with more mass would gobble up substantially more power compared to a light skinny wheel. More massive wheels might be more dangerous as they take more energy and time to spin up and down.

Still, ignoring some manufacturers obsession with higher speeds, this might be the way to go. Big wide low-pressure tubeless tires, massive motors and axles, and bigger batteries with power to spare...but piddling range. I basically see the rise of SUV wheels which to me is a good thing but hopefully riders like @Marty Backe  will have a longer-ranged option.

[LanghamP]

On 8/14/2017 at 5:02 PM, Marty Backe said:

No offense taken. We're just talking.

I fully realize that everyone has differing opinions about the various manufacturers and the wheels that they make.

I'm OK with Gotway and will continue to buy their wheels. If I agreed with your statement "literally falling apart underneath you" then I most assuredly would not buy any Gotway wheel. But I think as a whole they work very well.

Your statement about the batteries is interesting. Can you provide specifics? I'd like to know what Gotway has done, and how you know it.

But you had a Gotway literally fall apart under you! Twice! Maybe more. Aren't you a bit wary of Gotway?

[Tomek]

some more pics, borrowed from here https://evnerds.com/electric-vehicles/e-unicycle-hoverboard-news/ninebot-one-z-models-and-ninebot-no-9-at-beijing-segway-store/

 

whether the fat tire's practical or not, time will show. but it looks badass. I want!

(on the second pic, btw. you can see that it has a "sharp" profile, perhaps especially made to make it as manoeuvrable as the regular EUC tires)

Edited August 16, 2017 by Tomek

[Mono]

1 hour ago, LanghamP said:

I'm convinced that a tire/wheel with more mass would gobble up substantially more power compared to a light skinny wheel. More massive wheels might be more dangerous as they take more energy and time to spin up and down.

Compare the added mass from a wide tire with the rotating mass the motor and rim have anyways (of course mass times diameter). I am pretty sure your finding will be that it doesn't contribute a lot.

I have been a pretty vocal advocate for weight reduction of EUCs since ever, but I don't quite see the point in being too picky about tire weight. That said, I assume the new tire weighs less than 2kg.

Edited August 16, 2017 by Mono

[LEO_LEO]

...this model remember me the fat-bike solution: all terrain, more grip and shock absorber in one side, more resistence to rotation in other side, but better than a bike because with the euc the defects are solved from motor and batteries

[meepmeepmayer]

Not sure if such a wide tire even makes sense. From the looks of it, only the center circumference will actually touch the ground on any but extremely soft surfaces. Are such tires commonly used for some application?

A standard, big profile mountainbike-like tire (not sure what it is) like @Joey Serrin uses might be better for offroad in the end (but of course has much higher rolling resistance than the more road-tire-like one on the Z).

But who knows, maybe this tire makes sense, looking forward to impressions of the Z in the wild!

[Marty Backe]

2 hours ago, LanghamP said:

But you had a Gotway literally fall apart under you! Twice! Maybe more. Aren't you a bit wary of Gotway?

The ACM is the only Gotway wheel that has failed (fall apart, using your words) on me while riding, and that was under tough conditions. I'm not happy about it, but there was no mystery involved.

Every thing that has happened to me regarding Gotway wheels has been fully understood and resolved. It's not like they randomly "fall apart".

I still ride all my Gotway wheels with gusto, and just bought another one actually 

[electricpen]

2 minutes ago, Marty Backe said:

I still ride all my Gotway wheels with gusto, and just bought another one actually 

 

Did you join the Mten club??

[Marty Backe]

54 minutes ago, electricpen said:

Did you join the Mten club??

[steve454]

3 hours ago, Tomek said:

(on the second pic, btw. you can see that it has a "sharp" profile, perhaps especially made to make it as manoeuvrable as the regular EUC tires)

I just noticed that, it looks like the width of a smaller tire is all that will touch the ground.  Maybe as some others have said, the wide tire is designed as suspension.

[ir_fuel]

3 hours ago, Mono said:

Compare the added mass from a wide tire with the rotating mass the motor and rim have anyways (of course mass times diameter). I am pretty sure your finding will be that it doesn't contribute a lot.

I have been a pretty vocal advocate for weight reduction of EUCs since ever, but I don't quite see the point in being too picky about tire weight. That said, I assume the new tire weighs less than 2kg.

 This requires calculation as mass which is situated so far from the center of rotation will have a huge influence.

[jojo33]

...

 

 

 

Edited August 16, 2017 by jojo33

[Mono]

On 16/08/2017 at 7:47 PM, ir_fuel said:

 This requires calculation as mass which is situated so far from the center of rotation will have a huge influence.

It seems you overlooked this little "(of course mass times diameter)" thing.

The funny thing though is that there is a simple model to get an upper bound on the relative importance of the moving mass compared to the fixed mass. I found it in an article on bicycles discussing this very thing a while ago. 

The wheel diameter is at most moving twice as fast as the fixed mass. The point at which it is moving twice as fast is exactly the top of the wheel. (The tire contact patch midpoint is not moving at all relative to the ground.)

The rotational speed of the outer diameter of the wheel is of course the same as the speed of the EUC.

The implication is that the importance of the moving mass on acceleration or agility is very much overrated.

EDIT: maybe the conclusion was not entirely clear: it means that adding 400g to the tire cannot be worse than adding 800g to the shell in any regard.

Edited August 17, 2017 by Mono

[jojo33]

Ok

@zugu

Zugu Just said me  Z10 weight is 22 kg  48 lbs 

From mister Cid Wang 

Edited August 16, 2017 by jojo33

[electricpen]

Just now, jojo33 said:

Ok Zugu Just said me  Z10 weight is 22 kg

From mister Cid Wang 

Pretty light for an 18" actually. Especially with the big tire.

[Mono]

1 hour ago, electricpen said:

Pretty light for an 18" actually. Especially with the big tire.

22kg is out of my league, I am saddened