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ESP (Electronic Stability Programme)

自 Renault 再度在台銷售以來，從 Clio Sport 172 之後引進的每一部 Renault 上均搭截了 ESP，這個翻成中文叫「電子穩定程式」的東西，顧名思意目的在於穩定車身動態。簡單地說，ESP 是 ABS 防鎖死煞車系統的延伸，這支程式依據車速、方向盤角度、方向盤角速度以及四輪 ABS sensor 傳回的訊息，判斷車輛是否處於不穩定的狀態，當不穩定狀態被判讀時，ESP 便介入導正車身動態。

由於可能產生的車身動態有很多種，ESP 會依據不同的狀況下達不同指令，而這些指令大致是節制電子節氣門角度 (即 MSR，主要功能在抓地力不良的路面縮減引擎轉速降低扭力輸力以便容易控制車輛) 與不同程度的各輪獨自煞車的組合。當 over steering 狀況發生時，便會命令外側前輪或內側後輪煞車 (或同時)，藉以改善車尾向外擺動與車頭過度向內切的狀況，反之當 under steering 狀況發生時，則以相反的方式導正，這便是所謂的 under steer control，而整體而言，這便是 ASR traction control 循跡系統。

關於 under steer control 的部分，不但有助於行車安全，同時亦有增加操控樂趣的功效。對駕駛技術普通的人而言，轉向過度的設計是較不安全的，因此一般較保守的家庭用車製造商，傾向於將車輛特性設計成較為轉向不足 (即使是高級後驅車也往往有這種現象)，但轉向不足並非在所有的路狀之中都是好的，有時 over steering 反而能在較高車速的情況下避開突發的危險，當然同時也等於擁有更強的過彎能力 (不過大部分人都不擅於開快，對開快也沒有興趣)，因此在將車輛設計成較安定的特性時，若能藉由 ESP with under steer control 輔助不時產生的需要，將是一個非常完美而實用的方案。

Renault 所使用的 ESP 是由 Bosch 所研發的系統，最早在 1995 年時只搭載於 M.Benz S class 與 BMW 7 series，而最新的 Bosch ESP 系統，每秒鐘可以分析所有數據高達 25 次，提供最主動而即使的安全措施。此外，當 ESP 強烈介入時，由於電子節氣門的關閉使得引擎動力輸出銳減，加上可能高達四個輪子同時急劇煞車的情況下，車速瞬間降低可能會造成後車追撞，因此在此時煞車燈會自燈亮起提醒後車駕駛，由此可理解 ESP 是相當人性化的設計。

下面是 Renault 官方公佈之 ESP 詳細解說。

ESP with understeer control

What it is

Electronic stability programme (ESP) helps the driver to maintain their intended course should the vehicle veer off-course during an emergency manoeuvre, but never assumes control of the vehicle. A special new function optimizes ESP when extreme understeer occurs in emergency cornering situations (when the front wheels lose their grip and the vehicle heads for the outside of the curve). The supplementary ASR traction control function works when starting from rest and during acceleration.

How it works

Whenever a deviation from the intended course is detected, ESP induces a correction by reducing engine torque and braking one or more wheels in order to return it to the intended trajectory. ESP with understeer control differs mainly insofar as it has a more highly developed control program. Apart from oversteer, the new computer deals more effectively with extreme understeer or loss of steering control through lack of front wheel grip. Correction is then applied by reducing engine torque and using the braking system to reduce speed. Understeer control works on the two inside wheels, or on all four wheels together depending on the severity of understeer. Since it is capable of creating strong deceleration, operation of the understeer control is accompanied by automatic illumination of the stop-lights should it apply braking to all four wheels, so as to warn following vehicles. It should be noted that even when understeer control is in action, the driver can still increase braking if necessary.

An ASR traction control function for starting from rest or accelerating in low-grip conditions completes the ESP system features. The computer permanently monitors any difference in rotation speed between the four wheels. Whenever it detects that one of the driven wheels is beginning to spin, that wheel is braked in order to transfer part of the torque to the opposite wheel. At the same time, thanks to the drive-by-wire accelerator linkage, the engine torque is reduced. In Mégane II and Scénic II, this function can be inhibited below 50kph by means of a dashboard-mounted switch, to facilitate starting from rest on unmade or uneven road surfaces. It is automatically reset each time the engine is started, whenever the driver brakes, or when the speed exceeds 50kph. Finally, the engine torque regulation on overrun (MSR) function prevents locking of the driven wheels by controlling the engine torque output when the accelerator is released or during deceleration on low-grip surfaces.

Received wisdom

While ESP with understeer control intervenes effectively in emergency situations of low grip or when cornering, it cannot provide total safety if the speed is much too high. The driver needs always to remain conscious of their speed and adjust it when approaching a potential hazard.

Renault status

ESP is standard or optional according to version on Clio. ESP with understeer control is standard or optional according to version on Mégane II and Scénic II, Laguna II, Vel Satis and Espace IV.