Limitations of feedforward control in multiple-phase steering movements

Abstract

When attempting to perform bi-phasic steering movements (such as a lane change) in the absence of visual and inertial feedback, drivers produce a systematic heading error in the direction of the lane change (Wallis et al., Curr Biol 12(4):295-299, 2002; J Exp Psychol Hum Percept Perform 33(55):1127-1144, 2007). Theories of steering control which employ exclusively open-loop control mechanisms cannot accommodate this finding. In this article we show that a similar steering error occurs with obstacle avoidance, and offer compelling evidence that it stems from a seemingly general failure of human operators to correctly internalise the dynamics of the steering wheel. With respect to lateral position, the steering wheel is an acceleration control device, but we present data indicating that drivers treat it as a rate control device. Previous findings from Wallis et al. can be explained the same way. Since an open-loop control mechanism will never succeed when the dynamics of the controller are internalised improperly, we go on to conclude that regular, appropriately timed sensory feedback-predominantly from vision-is necessary for regulating heading, even during well-practiced, everyday manoeuvres such as lane changing and obstacle avoidance.

Sensorimotor basis of motor vehicle control

“…As a result, it is not surprising that, without special training, drivers develop a wrong internal model during daily steering through their "naïve physics". Previous work (Wallis, Chatziastros et al 2002, Wallis, Chatziastros et al 2007, Cloete and Wallis 2009, Xu, Wallis et al 2014 shows that for a normal, acceleration device drivers keep making systematic errors during lane-change without visual feedback. This suggest that steering cannot be simply regarded as either an open-loop model or closed-loop model.…”

“…The results, at least, the majority of participants attempted to produce a second, return steering phase when parallel parking in no visual feedback condition. This is interesting because it suggests that the naïve understanding of vehicle control seen in subjects driving forwards and conducting tasks such as lane change and obstacle avoidance, does not replicate to the case of reversing (Wallis, Chatziastros et al 2002, Wallis, Chatziastros et al 2007, Cloete and Wallis 2009, Xu, Wallis et al 2014. Future work should aim to fully investigate whether disappearance of this erroneous steering behavior is due to a different internal model being harnessed during reversing.…”

“…The fact that a uni-phasic 4 manoeuvre can be conducted without feedback but a bi-phasic manoeuvre cannot, suggests that drivers require feedback to generate a second steering phase. However, recent work from Wallis' lab suggests that drivers are able to conduct a lane change without visual feedback, but only if they are asked to do an obstacle avoidance manoeuvre (Cloete and Wallis 2009). Since obstacle avoidance involves two lane changes, with the first one to avoid the obstacle and the last one to return to the original lane, it can be essentially treated as a tri-phasic manoeuvre (the last steering phase of the first lane change merges with the first steering phase of the last lane change).…”

“…Wallis and colleagues have shown that a uni-phasic manoeuvre of roughly appropriate amplitude and duration can be conducted without the need for any visual feedback at all (Wallis, Chatziastros et al 2007). What Wallis and colleagues work also reveals, however, is that a minor increase in task complexity, to a biphasic manoeuvre, suddenly produces systematic errors in the absence of visual feedack (Wallis, Chatziastros et al 2002, Wallis, Chatziastros et al 2007, Cloete and Wallis 2009, Xu, Wallis et al 2014). …”

“…However, Cloete and Wallis showed that if drivers are asked to conduct an obstacle avoidance manoeuvre, they produce a lane change instead! This would seem to imply that a drivers' spatial memory is capable of supporting a lane change without feedback if the driver chooses to implement the biphasic steering-wheel movement (Cloete and Wallis 2009). Rather than accounts based on memory, recent papers on the topic have concluded that the problem instead lies in the fact that drivers conceptualize the steering wheel as a rate control device for lateral position, rather than the acceleration device that it really is Wallis 2009, Xu, Wallis et al 2014).…”