PicoScope NVH episode 1: An introduction

PicoScope NVH episode 1: An introduction


hello and welcome to this joint presentation between pico automotive and adsr to inform I’d like to introduce Steve Smith from pico and myself Frank Master from ABS the subject today is NVH noise vibration harshness an incredibly fascinating subject and I’m sure you’ll agree an incredibly useful tool given the development of the mechanical systems on vehicle absolutely Frank I think the more you dig and delve into MBH the you’re on a journey that’s for certain the beauty of MBH with picoscope is the non-intrusive fashion in which we can diagnose numerous components as you’ll see over the next seven or so videos yeah it’s a challenging subject the capture of vibration and noise is relatively straightforward nothing is easy I think you said that so many times before but the analysis techniques that we can do with picoscope that certainly brings it to life that really makes us or helps us diagnose these problems yes I think without further ado let’s let’s begin with section one as introduced and the edge okay Frank NVH noise vibration and harshness acronym is NVH of course noise is defined as an unexpected or unpleasant sound in the wrong place at the wrong time it sounds obvious doesn’t it really but we start the vehicle in the morning the engine we accept will make some form of noise some form of vibration but should we develop a knocking noise from that engine at a specific frequency that becomes a real issue and that becomes a true customer complaint complaint of noise I think we focus on the fact that the motor vehicle essentially is a series of mechanical components that are constantly in conflict with each other things that go around and things that go up and down never are going to be harmonious we have to understand the difference between what is normal and correct and what is a fault yeah and certainly every edge will allow us to do that because that you’ve just hit on something there what is normal what is correct well these characteristic it’s very easy to convince yourself that there is a problem when in fact this is a characteristic of the vehicle so to be able to conclusively measure that incredibly flowers I will compare it with an unknown platform yeah a known good vehicle yes yeah yeah vibration then is defined as an objectionable repetitive motion of an object and this is either back and forth so for a now up and down or left and right lateral the three axes of vibration you’ll hear that term a lot over the next few videos three axis of vibration I think of a tire with a excessive lateral run-out that would affect the vehicle in a lateral direction and we can measure that vibration in that axis only as we can in the other axis so my understanding of my simplistic understanding between say noise and vibration is noise can be a singular event multiple of them but singular events with vibration it’s repetitive it has really say its amplitude most certainly which can change yes when you drive the vehicle and it will change yes but there’s nonetheless it’s repetitive yes yeah numerous factors certainly speed as we come to do Road testing road surface vehicle settings I mean you’ve mentioned this a number of times about when we looking for vibration we must must make sure that we’re driving that vehicle exactly as the customer would drive the vehicle mode suspension settings absolutely and I think also from point of view of the workshop you must choose a piece of road that is your testbed and stick to that piece of road otherwise you’ve not got a level playing field yeah it’s about removing all the variables yes I think it may be if we have to drive on the road that the customer experiences experience is the problem then we’ll have to yes that’s how yes it could be a particular piece of road surface which is an issue and we have to take that into account that road surface doesn’t have to be potholed or roughing maybe the texture of that road surface is generating a tyre noise which for all counts and purpose is not a problem with the vehicle correct yeah yes so that’s what we can qualify here yeah and then finally harshness is defined as a certain aggressive suspension feel lack of give to a single input so that would be a pothole that would be suspension bottoming out a real harshness between the road surface and the steering wheel for example you’re feeling that whole event being transmitted through into the cabin steering wheel floor pan seat however you’re connected with the vehicle so you’re suggesting there that harshness perhaps is a relationship between the environment the vehicles operating in and how the vehicle responds to it and the vehicle instantaneously responds to an event yeah knocking events in suspension these singular events they’re a real nuisance trying to diagnose them it’s challenging subjective at best unless we can measure yeah but again we’ll tackle harshness as we move through I think that technicians have always described noise vibration harshness based on opinion never on fact what MBH does as a as a tool it presented the facts yeah objective results yeah we’ll look at the different frequencies involved with noise and vibrations and there is a gray area where we’ll experience either noise or vibration differently I mean I made you’ll be to the car and I can hear a booming noise you jump in the car you think well I can feel something we’re talking about the same thing in effect yes and we have to accept that humans have different hearing capabilities yes so so yeah the customer has one opinion yes but will be objectively measuring those yes so that’s the real benefit here within the edge so in a series of videos will aim to show real-life examples of the tool in action looking at cabin noises that might be rattles creaks squeaks knocking noises suspension issues this is a real this is quite challenging for intermittent noises from suspension but of course we know how to tackle these now revised techniques that we’ve sort of developed over the last couple of years engine noises propshaft imbalances that’s not necessarily proper that might be driveshaft anything that rotates on that vehicle there’s a say anything that shakes vibrates or make noise we can capture those with MBH wouldn’t be a good idea for the technician to have and we’ll call it a process a means of driving that is a laid down process which he can repetitively follow us how we accelerates how we break sorry operates the steering yeah so that it’s an objective platform from which these results are obtained yeah I think you mentioned a test route having a test plan taking into consideration the customer complaint that most certainly let the customer drive the vehicle in their scenarios that’s that’s I think essential yeah yeah take that vehicle I try and simulate as much as you can the customer complaint the conditions yeah but a test plan essential especially if you’re not going to see the customer there’s always that isn’t there that the car is dropped off have a test plan a driving technique and we’ll talk about Road test techniques as we move throws off but certainly selecting neutral will allow the engine to idle down but we can maintain road speed so we can separate engine from from engine from road speed vibrations okay so why do we need NVH so we’ve talked already customer complaints on the increase and this is I think borne about by hybrid and v’s and just vehicle interiors in general the cars are aiming for the the optimum driving experience on minimal noise minimal intrusion so any inkling that there’s a noise in the cabin or the vibration passing through this there’s upset there’s a concern from the customer cost-effective demand for a solution I think traditionally NVH has always been an expensive tool I mean II think there are some incredible NVH tools out there on the market costing thousands and thousands of pounds and and then additional cost for software as well certainly you see them in research development and manufacturing I mean these are the kind of tools we’re talking about but think about you’ve got a picoscope already that MBH is an accessory to that tool to picoscope for measuring noise and vibration ability record playback vibration and sound data this is them this is a real when I’m passionate about this and this is capturing these customer complaints capturing the event you’ve got objective results you’ve got proof you need proof you know why I might changing this component is the the noise that I’ve captured is it a characteristic is it normal yeah what what has drawn my attention to that specific area yes yeah yes so this is the speed that the customer was driving and this is the engine speed and this is a sound that I can hear and this is the frequency will capture this all with MBA you’ve touched on this already Frank back to back testing yes Harrison testing you’re in a world of pain if you start rectifying or attempting to rectify characteristics yes you see time and time again we need to explain to the customer that the car is behaving as designed that you know the frequencies the noise that we can hear what he can feel is completely normal we I think at this point also make an issue where has the vehicle being modified has the customer put different wheels different tire sizes yeah change the power outputs of the engine changed the suspension geometry we might be trying to fix a fault that has inherently now been built into the vehicle I think we stand here and we say back to back testing like it’s easy to do like we can just go outside and find an identical vehicle and drive that at the same speed and and and everything’s fine but the second you just changed tires on a vehicle for a different brand having is changed the variables have just gone through the roof haven’t they yes so there has to be a tolerance between vehicles but yeah this is all about I’ll call it get-out-of-jail testing really back to back testing we can still prove the the area of concern the component of concern but then we have to build in the the the unknown yes yeah the classic on this brings to mind was customers coming out of conventional injection gasoline injection engine vehicle into direct gasoline engine just the noise generated from those injectors a customer was absolutely convinced that he had a tapping noise yes he was convinced but to be able to record the noise level from one vehicle and another we were able to put that to bed very quickly accurate identification and vibration and sound source you’ll see as we move on that the software will pinpoint specific known vibrations so we’ll know the tire frequency we’ll know the frequency of the prop shaft or the engine and if the amplitude of those is excessive we’ve clearly identified what it is that’s vibrating but probably more importantly we vibrate identified what is not vibrating how important is that diagnostics is a series of test failures before you find the actual responsible component you look at it in a negative way yes you’re ruling out what it isn’t and yes going down filling out what it isn’t to arrive at what it is yeah yeah I think we’ve all been there with these vehicles Road testing and we all have an opinion of what we think it is but to be able to quickly say it’s not this or this component so now we’re left with two others it is a godsend agreeance traffic there is customers had the wheels bow on several times it can’t be wheels it can be inspected before and after the fix for customers something you mentioned to me Frank about carrying out modifications to customer vehicles they want superior handling so they want performance shock absorbers they want the suspension allowing lowering so are they aware what’s going to happen to their vehicle in terms of ride quality you know we need to perhaps measure before measure after for modifications or of course before fix and after fix to qualify repair yeah objective test results proof you’ve got proof we all have an opinion of what we think it is but can you argue with the science with the measurement the confidence from from the technician in progressing into the repair of that vehicle is based on evidence really is so here we have an animation then of NVH and how we interpret these terms so we have the bobblehead on the dashboard everything is fine music is play no noise no vibration no harshness develops no it’s developed just how uncomfortable that can feel inside the car I guess here we’re talking about the perception different frequencies different levels of noise exactly some of which can be other voidable such as road surface there we have harshness yeah between those certain impacts and how they affect the vehicle and they affect the occupants of a noise wind noise are big big I think we all have different tolerance levels as well it’s amazing you join me the customers cars and you hear this noise vibration won’t it feel this vibration and the customer has no perception at all that’s quite normal to them what is some what it what what qualifies a customer complaint ok so what would you need to measure NVH well we have here the standard essentials kit that includes a four channel scope it also includes two microphones two accelerometers you’re also gonna need the software pica Diagnostics so MBH is contained within the free software and of course how do you display how do you capture or how do you review your results well with the screen here this is the bar graph screen that you’ll see from the peak of diagnostic software and I believe the software has a license which is given freely on purchase that’s wrong as we move through you know if it’s some whenever you purchase an NB h kit you were required to obtain the serial number of the scope and the serial number of the interface and that will release a license key that will then unlock your scope for nbh so it’s not these PC that you unlock it to the scope so that’s go can then travel anywhere shared with anyone to measure NVH good point frame actually is that you don’t need a scope or an in the H kit to view NVH files the software is free you can nip on to the forum read some case studies open up the NVH files zoom view change the views highlight different areas the software will allow you to do numerous operations arbitrary measurements from a pre saved file so for example you go to the forum for a case study of a prop shaft as long as they have posted the NVH file and you have the picoscope software installed on your pc it will open be able to see exactly that road test any recordings that were then at the same time as well they’ll all be there ok so the scope kits three kits starter standard and advanced so it’s a starter kit for channel scope this is the essentials if you don’t if you already have a bigger scope sorry you don’t need to buy any sensuous kid because anything with the word essentials in there exam determines that there is a four channel scope in the kit if you buy a starter NVH kit that’s everything in the kit except the scope so if you’re already pico owner so if you’ve got this hardware yes you can buy just the essentials with mdh choose the accessories accessories and the word essentials determines that there’s a scope in what KTM and right is saying it can be a two channel scope yes or a four yeah okay in our kids everything essential is for channel if you have a two channel picoscope you’re not penalized in any way you’ll see as we come to do measurements that if you want you to do a three axis measurement that you’d have to choose two of those any two of the three any two of the three axis yeah um we’re going to focus all our Road testing all our descriptions over the next few videos on the standard NVH kit yeah because within there we get two microphones two accelerometers and the benefits of which ranked pretty obvious in that you can minimize the amount of rotor having you down a bit and for example a customer complained of vibration with the starter kit you’d have one accelerometer or a microphone connected you do one row test and obtain a vibration and it may be that you want to do a second row test you’re going to have to position that accelerometer try and reproduce your variables or minimize you variables by doing exactly the same with the road test just increases your diagnostic time to be able to have an accelerometer mounted on the floor on the seat frame and then another accelerometer maybe in the engine bay in one road test we’ve captured two zones of the vehicle and perhaps just bear in mind that when you drive a vehicle the tires warm up that could change the whole thing again so you the amount of error subject to endless yes yeah and we need to be aware of yes yeah you know I must we be put off by these being aware I think in powers yes most certainly finally the advanced in BH essentials kit so again essentials would mean there’s a four-channel scope in there you can still buy this without the scope for channels for accelerometers for microphones any combination could be great for that initial road test of an accelerometer placed on all four corners of one road test yeah one capture you know the ultimate starting absolutely yeah yeah yeah so for microphones as well or any combination it may be that we’ve got a noise or a vibration we’re not sure which let’s have an accelerometer on the driver’s seat accelerometer front and rear and maybe a microphone in the cabin yes you touched on something here about narrating Europe absolutely if you’re driving the vehicle and an event was to take place or an observation make the observation vocal record within the the tape an observation you’ve made if you wanted to reproduce it or discuss it later or replay it in the workshop you’ve got the notation actually on the tape yeah I like the point of narrating the rotors because it may be that you’ve just hit an incline and you’ve kept your foot on the gas pit perfectly still so then the load characteristics have changed on the vehicle I think maybe something the actual owner of the car actually says it helps you in the process oh yes yeah as you open up that rapport with the customer and the trustees building you absolutely so here is the NVH essentials kit two of everything two microphones two interfaces two accelerometers if you’re going to connect anything to this picoscope it has to go via an interface so well here microphone this microphone screws into an extension cable best position ideally for the microphone is wherever the customer is complaining if it happens to be readjust that can hear the noise let’s put the microphone by the rear passenger otherwise generally that would sort of hang got ground by the rearview mirror yeah and that would be capturing all that cabin noise if it’s going to connect to picoscope it must go through an interface so whatever accessory it may be if it’s an accelerometer or a microphone it must go through an interface the accelerometer this is a three-dimensional accelerometer which has a a very powerful magnetic base so it will attach to anything this is ferrous base and once the game goes through the interface yes before it goes to scope plenty of lead lengths have had no no issues there with reaching different areas within the vehicle so you haven’t that found that you wash as an extension lady in the kit you haven’t had to use one so far deal that’s good and how would that connector picoscope well there’s our interface it’s XY and said of the accelerometer goes to a BNC of picoscope accelerometer would connect into here and there you are that pretty much is your connection for a vibration measurements I really don’t think it gets any less intrusive you know certainly from a customer complaint is attached to the seat she’s generally the driver who’s complaining yeah we’re dealing with the complainant as the driver there for yeah we assume that let’s assume that we’re collecting the data from the point where the complaint has been exact Oh totally yes so here we’ll have a road tester just how we would carry out our initial vibration using the standard MBA essentials kit there’s that components within the kit 3-axis measurement so X Y Z ABC you see there we have a mongoose lead we’ve chosen mongoose lead to connect into the diagnostic connector our accelerometer mounted onto the seat frame and it’s essential that for our first road test if it’s a three axis measurement and we want to identify the offending axis that we mounted vertically with the screw thread through thirties in the front of the accelerometer screw thread facing forward so that would be our orientation for our first measurement but there is there is a map a map have the three dimensions actually on the device as well yes directional map which it’s best orientated correctly in the vehicle the mongoose this is our chosen J 2534 interface this allows us to connect into the vehicle diagnostic connector and request three pieces of information engine speed road speed and chassis number VIN number yeah depending on the vehicle we don’t always get VIN number and there’s often not so much an issue but sometimes they’re through the protocol but we can’t obtain it the software will explain that or it will be build identify that it cannot detect the VIN number so it would be a manual entry amiright also saying in fairness if you’ve got a pass-through device that you can use that pass-through device to obtain the same information yes to work with MBH so if you have another diagnostic tool utilizing J 2534 protocol passed through as long as it’s software is installed on your PC the drivers are installed and mvh will search for that device then use that to obtain engine speed and road speed the Mongoose is not included in any of the kits it is an accessory over and above an essentials kit if you’re a specialist company like we’re on V AG range of vehicles that particular company does a higher level of interface profile with yes this would be Mongoose for the AJ yes yes absolutely yeah as a specialist company you might consider that as being an option you might want them to take I know from the brand that I know is a Toyota Lexus exactly the same monkeys optimized for Toyota Lexus pass-through device will work with your NVH kit so we’ve had the opportunity of a overview of the hardware with the mvh kit and I think you’ll see that the application of the hardware and itself is very quickly connected to the vehicle the next section is I think crucially important and this is the theory of mvh we must have the understanding of what it is we’re actually capturing and to understand the fare is important to be able to relate it to certain functions within the vehicle so the next section is the theory of envy edge


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