New High Resolution Sonar Line from MaxBotix: HRLV

Our friends at MaxBotix have updated their offering of ultrasound sonar sensors by adding the new High Resolution LV line. The defining characteristic of this new line of sonars is the 1mm resolution. Yes. 1mm. Well, more correctly, "the HRLV-MaxSonar-EZ Sensors offer calibrated 1 mm accuracy of 0.1% at 1 meter," so at greater distances, the ranging might be off by a millimeter or more. Up to 5 millimeters at 5 meters, if the accuracy were linear. I can live with that. *grin*

 

The new sensors offer a similar near end range, a minimum of 30cm, and the data sheet describes a 5 meter maximum range. This is slightly shorter than the 6.4 meter maximum range of the LV line or the 7-10 meter range of the XL, but my thinking is beyond 15 feet off the deck, you might not notice if your multicopter switches to using the barometer for alt_hold. Like the other product lines, the specifics of range are most likely subject to the beam pattern. As with the LV line, it is available in a variety of beam patterns off the shelf, and they offer custom solutions for customers who require it. 

 

This new sensor line offers the same interface as existing sonar products, including analog, serial/TTL, and pulse width, comes in the same form-factor we to which are accustom, but the manufacturer provides details on additional distinguishing characteristics of this new line over the LV line, including:

 

  • Higher resolution output
  • Automatic calibration of, noise, humidity, and voltage for consistent, long term, operation.
  • Automatical compensate for speed of sound changes due to the effects temperature changes
  • Advanced firmware to handle a variety of noise sources
  • Simultaneous multiple sensor operation
  • Noise filtering is even better than previous MaxSonar products
  • Automatic target size compensation

With this level of resolution, I expect there are new technical challenges related to air temperature changes in near-real time, and this suspicion is somewhat supported by two features of this sensor. First, there is it's onboard support for compensation of "self heating" through an onboard temperature sensor. Second, there is support for an external temperature sensor, also available from MaxBotix, which when combined with the onboard temperature sensor, can eliminate a potential "drift of ... up to 3%."

The product page also reports that the HRLV are designed to support simultaneous sensor operation, but it is not clear from the initial information if this is handled through time triggered operation, as with the other sonar lines, or if this sensor discriminates between its pulse and those of other nearby sonar units in some new fashion.

Here are the beam patterns available off the shelf. 

There are a range of other features worth discussing, but let me not distract you from the important questions. Or rather, the important question. With this type of high resolution, I would expect this sonar to come at matching high price. Like the LV and XL lines, different sensors are priced differently, but t The lineup is advertised at MSRP $28.95 - $34.95 for a single sensor, with volume discounts available.

I should mention right now that I have no ties to MaxBotix, except as a fellow customer. I don't get any discounts by bringing this news to you, and at these prices, I don't really need any (but I'd gladly go in on volume purchases if anyone wants to organize some, hint-hint 3DR team.) I was notified by email about the new line in a product announcement email. And that is important to this audience because it also informed me of another useful bit of information. These sonars are begin offered at a 25% discount until 7/15/2012 if you use the discount code en4v en4V [the code is case sensitive.]

A quote included with the product announcement (not attributed):

“1-mm resolution is so stable, that when measuring typical objects at a distance of one meter, the readings do not change by more than 1-mm.”

See the linked data sheet or the product Web page for more information.

 

Views: 3879

Comment by Jack Crossfire on June 14, 2012 at 10:04pm

5 years & the cheapest one is still $26.  Wish they could be made smaller.


Moderator
Comment by Michael Pursifull on June 14, 2012 at 10:16pm

Jack, you're a hard person to please *wink* If I recall correctly, this is the level of accuracy found with the Vicon systems used at ETH in the Flying Machine Arena (that system offering full 3d localization, of course.) 

The way I see it, five years and they just keep getting better. The form factor works for my purposes. In fact, I like that they all have the same footprint. It makes swapping them out and designing mounts and cables for them easier. 


Developer
Comment by Randy on June 14, 2012 at 11:14pm

We'd have to slightly change the RangeFinder class to interpret the new output correctly but it's not too difficult really.  I guess I can read the datasheet...I wonder if it requires you to use the pwm output or if analog is still support and still provides that level of accuracy.


Moderator
Comment by Michael Pursifull on June 15, 2012 at 12:17am

@Randy - I had planned on hacking up a patch for consideration, but I can send you or Jason or another dev a unit for your own tinkering (on loan) when mine arrive. I get what you're saying about wondering about analog vs pwm and accuracy. I'd think that even if the sonar could support analog at that accuracy, we might have problems reading it on an arduino architecture. I seem to recall the resolution for analog sensors is 0 - 5v range supporting a total of 0 - 1023 provided from analogRead(). It the readings are linear and uniform, that only allows about 5mm precision in reading the value, twice as good as existing sensors, but not the x10 that the sonar is capable of. There is also TTL, but those are too valuable to tie up with a sonar, and PWM, well, no one likes their gear falling out of the sky on a blocking call ;) Good question to raise. PM me if you want me to send you one to play with when mine arrive. 


Moderator
Comment by Michael Pursifull on June 15, 2012 at 12:28am

Even 1/2 cm would be an improvement, potentially, wouldn't it? I'm thinking along the lines that a 1cm resolution means the alt_hold is likely to have +/- 2 or 3 cm before the PIDs can generate an error, and the best hold that could theoretically be achieved is on the order of +/- 3cm, most likely more. I'm speaking way outside my comfort zone, but that seems logical. With 1/2 cm resolution, that takes it theoretically down to +/- 1.5cm, I'd think that would at least "look" a lot tighter, or at least give the PIDs more purchase in terms of error. Then again, I recall most of the code uses centimeters as units to begin with, so I wonder about the cost of supporting a more precise value. 

Comment by MaxBotix Inc on June 15, 2012 at 8:41am

Hello! This is Scott from MaxBotix Inc. We are glad to hear that you are excited about this new product release. We wanted to clarify a few points that will help the DIY Drones community evaluate and use our products.

Before you purchase an HRLV-MaxSonar-EZ, keep in mind that the XL-MaxSonar-EZ/AE sensors still have greater output power then the HRLV-MaxSonar-EZ sensors. This means that the XL-MaxSonar-EZ/AE sensors have a greater ability to detect soft objects like grass and shrubs, they also have a greater signal to noise ratio. Which is important in environments with lots of sustained noise like prop-wash, motor noise, and wind.

All things considered, the HRLV-MaxSonar-EZ is still a more accurate sensor.

You are are correct in that accuracy is calibrated in our facility to 0.1% at 1-meter. However this occurs once during the lifetime of the sensor and happens in a controlled environment. Our data-sheet explains this further: “Accuracy is factory-matched at 1-meter to 0.1% providing a typical large target accuracy of 1% or better for most voltages and uses.”

The HRLV-MaxSonar-EZ has an internal temperature sensor, but if the sensor is at a different temperature than the surrounding air range readings can drift.

There is no simultaneous multi-sensor operation in the HRLV-MaxSonar-EZ models currently available for retail sale. However, the current sensors do have some tolerance of occasional noise sources. Other models are in development and we have no expected release dates at this time; but I can say, I think that the refresh rate for the planned products will not be suitable in a multi-copter application.

Additionally, the sensor does have a 2Hz filter that helps make sure the sensors readings are accurate, which is applied when the sensor is running the default “Real-time Free Run Operation Mode”. You will have to evaluate if it is best to use the 2Hz filtered data or to run the sensor in “Real-time Triggered Operation Mode”, and handle the processing yourself.

I hope this additional information helps you with the use of our HRLV-MaxSonar-EZ sensors. If you have any additional questions please don't hesitate to contact us, we are here to support you.

Comment by Rob_Lefebvre on June 15, 2012 at 9:00am

Hi Scott, thanks for coming here.

I was going to ask about noise tollerance, but you've already answered that.

I have a question about the noise tollerance...  if there is excessive noise preventing the sensor from hearing the return, what happens?  Does it assume maximum range, and therefore output maximum range?  Because that is signal I'm seeing.  90+% of the returns are at maximum range, and only occaisionally a blip gets through.  Does this agree with your noise testing?

I'm using it on a large electric heli, and I'm pretty sure the noise level is above 94dB.  I have tried the MB1200 and the MB1260.

I'm probably going to try an MB1240.  Is the maximum range of the 1240 the same as the 1200, but it is just less sensitive?  I just want to know if the input scaling for the 1200 will work with the 1240.

Comment by MaxBotix Inc on June 15, 2012 at 9:25am

If there is a large amount of noise, it will cause the sensor to not get the proper range readings to the intended target. This will cause the sensor to return maximum range readings. You state that you are using the MB1200 and MB1260 on an electrical helicopter. Have you made sure that there is no electrical noise entering the sensor using a 10ohm resistor inline with the V+ and a 100uF capacitor in parallel of V+ and GND? You will also want to view http://maxbotix.com/articles/012.htm (Noise Tolerance Report) for information on the noise tolerance of the XL-MaxSonar-EZ Sensors.

If after checking for electrical noise and verifying outside acoustical noise the sensor still reports maximum range, you may need to switch to the MB1240 sensor. The MB1240 sensor is the least sensitive sensor in the XL-MaxSonar-EZ line to outside acoustical noise sources. If it is needed to change to the MB1240, all of the scaling is the same for the AN output (Vcc/1024)=mV per cm. It is also the best sensor if your looking to range only to large hard targets. Please email me at scott@maxbotix.com if more assistance is needed.   


Moderator
Comment by Michael Pursifull on June 15, 2012 at 9:26am

Scott, can you tell us something about the scaling used in the HRLV units?

Comment by MaxBotix Inc on June 15, 2012 at 9:42am

Lefebvre, you may also need to consider vibration noise being introduced to the sensor as well before switching sensors.  If it is possible, mount the sensor on a softer mount so the vibration is absorbed before it contacts the sensor.

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