Over a race distance, but we don't sell our system on that basis. The only saving comes from the extra time that the vehicle would beĪccelerating, which isn't going to add up to much over a period of 200ms unless you have a hyper-performance car! That's not to say that there aren't worthwhile savings to be made Track time saving of 200ms because the vehicle still has forward velocity during the shift. Even if the shift time was reduced from 200ms to zero, there would not be a corresponding So where does the saving come from? Of course there are no such like for like savings. Compared with what, exactly? 1/5 of a second is 200ms, which is actually longer than a decent driver will take to change gear using a stick! Of performance gains of 1/5 of a second per gear shift. While on the subject of shift times, we have read claims on one of our rivals websites (and rather amusingly, blatantly copied on another) Here and here, which clearly demonstrate the necessity for variable cut times. You can see some of our customer data logs using our closed-loop system Now, if you use a timer based (open-loop) shift system, how long do you set the cut time? Consider for yourself what the implications are if the timer expires and the engine power is resumed before the next gear has engaged. Typically we would see upshift times ranging from aboutģ5ms to as long as 150ms or more at the upper end. In the real world with the gearbox transmitting torque, the shift time can increase dramatically. This is the typical time that would be measured 'on the bench' with no load. On most gearboxes, this is in the order of 15-25ms. Show that in the ideal situation of a clean engagement with no transmission wind-up, the shift time is basically as fast as the pneumatic actuator can What you might not appreciate is how dramatic that variation can be. To complete can vary, depending upon various factors. So, we now know that the time it takes for the shift Suffice to say that the strategy to successfully get out of the current gear and engage the next one as quickly as possible is not just a case ofĬutting the engine or blipping the throttle for a few milliseconds and hoping for the best! The time it takes for the dogs to unlock depends upon several complex factors which are impossible to model or predict, A similar thing happens (but in reverse) on down-shiftsĭuring the throttle blip period. Tendency to keep the dogs locked together for a period of time after the engine power has been cut. This is due to a phenomenon known as transmission wind-up. Disengaging theĬurrent gear is the most challenging aspect of the shift. Both theseĮvents take a varying length of time to execute depending upon various dynamic factors acting upon the vehicle at the time. First we must successfully disengage the current gear, then we must engage the next gear. Here, as it will give the game away to some of our rivals who have yet to gain a full understanding of the complexities of sequential gear shifting.Īny gear shift, whether it's an up-shift or a down-shift, is a 2 stage event. However, I'm not going to go into exact details To get a better understanding of why closed loop control is necessary, we must first examine the basic mechanics of a gear shift using dog engagement. These highly developed control strategies are certainly not slow or out-dated, as claimed by one of our rivals, and they provide 100% shift reliability and optimum shift speed. An open-loop system applies the same engine cut or throttle blip duration for every shift, regardless of whether it is the correct duration or not.Ĭlosed-loop gearshift technology has been around for many years and the correct strategies have been well understood for some time by ourselves and a few others that are operating at the higher end of the motorsport market. Pneumatic actuator, engine torque reduction or throttle blip can be turned on and off as necessary to effect the fastest and most reliable gear shifts.īy contrast, an 'open-loop' system does not have any feedback mechanism and simply relies on fixed time delays for engine cut, throttle blip and shiftĪctuator operation. This information is fed back to the gearbox control unit (GCU) so that the Sensor to determine if and when a shift has been successfully completed. In the context of semi-automatic gear selection, the closed-loop system monitors the gear position The term 'closed-loop' refers to a control system that uses an electronic control unit in conjunction withįeedback sensors to modify its own operation in response to the sensor inputs - in real-time. Closed loop - what is it, and why is it necessary?
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |