Lateral acceleration is a key aspect of the vehicle response perceived by the driver. Assistance systems such as Active Rear Steering (ARS) or Torque Vectoring (TV) are developed to modify the lateral acceleration response such that the vehicle has an improved stability and an extended linear handling region. With this extended linear handling region the vehicle abruptly reaches tyre friction limitations (representing an entry into the vehicle handling limits (VHL)), this can potentially lead to dangerous situations. This thesis aims to quantify driver behaviour when being forced to drive near the VHL, in terms of how often the VHL is entered and what happens after entry. To assess this, a human factors experiment (N = 18) in a fixed base driving simulator was performed. In this experiment three different vehicle configurations were compared: (1) a conventional vehicle (Passive) (2) a vehicle with an extended linear handling region (Active) (3) a vehicle with an extended linear handling region and increased yaw response (Active Sport). In these configurations, the drivers need to drive with a fixed velocity on an oval track with Electronic Stability Control (ESC) switched off. It was expected that a conventional vehicle enters the VHL more often compared to the vehicles with an extended linear handling region. However, when entering the VHL, the vehicle with an extended linear handling region was expected to be more difficult to control due to the abrupt change in vehicle dynamics and corresponding steering feel. The results indicate that the Passive vehicle entered the VHL more frequently compared to the Active and Active Sport configurations. However, when the Active Sport configuration entered the VHL, significantly more road departures and an increased steering reversal rate compared to the Passive configuration resulted. Therefore, it can be concluded drivers enter the VHL less frequently in a vehicle with an extended linear handling region (caused by systems such as ARS or TV). However when the VHL is entered it is more difficult and dangerous for a driver to control compared to a conventional vehicle.

Drivers continuously adapt to the different needs and constraints in the driving scene. Literature has provided evidence for two adaptation strategies in response to an increased risk (decreasing the road width or increasing the driving speed) while lane keeping: decreasing driving speed and increasing endpoint arm stiffness. However, so far these studies did not investigate the interaction between the two adaptation strategies. The aim of this study is to find the interaction between drivers’ speed and neuromuscular adaptation for different risk durations. We hypothesize that the speed reduction is larger when the narrow road is longer which allows for a lesser increase in arm stiffness. Additionally, when the narrow road is shorter the increase in neuromuscular stiffness is larger and allows for a higher speed.
Twenty-six participants drove in a driving simulator experiment in a 1.8m wide car on a 35 km long road. Different levels of risk durations were imposed to the drivers on straight road sections by a road narrowing (from 3.6m to 2.2m) with a varying length (10m, 100m, 250m, and 500m). During the experiment speed reduction was measured and neuromuscular adaptation was quantified by measuring the grip force. Additionally participants subjectively rated their experienced effort from 1-10.
The results show that participants adapted to the road narrowing both by speed reduction as well as increased grip force, without significant impact of the length of the road narrowing. Only on the 10m narrow the speed reduction and increase in grip force was smaller compared to the other three cases. Interestingly, although drivers increased their subjective effort, no differences in speed and grip force adaptation were found between the three longest narrow roads. These results suggest that for narrow road lengths up to 500m drivers adapt their driving style to road width rather than road length. Future studies should identify if the identified speed and grip force adaptations also hold for longer and different durations of risk.

The aging society puts an increasingly heavy demand on the health care system. Elderly often have difficulties in mobility, reducing opportunities for exercise and social interaction that activities like running errands or shopping normally offer. This thesis proposes a novel concept for an assistive motorised shopping trolley, called Pull-E. Based on interview results with elderly (n=40) the Pull-E should be able to carry heavy loads (~20 kg) and still move easily and lightly while pulled over flat ground, curbs, and even stairs; and should ideally also be able to move autonomously, without being pulled. It should therefore have capabilities to balance itself, climb the stairs, carry items, and resist
perturbations.
First, a small proof-of-concept of the Pull-E was built, using tri-wheels which are separately powered by motors, that allow assistive stair-climbing when the Pull-E is pulled horizontally.
In order to balance itself the tilt angle of the trolley needs to be measured. Therefore, the Pull-E was equipped with a gyroscope and an accelerometer. From this prototype one of the most challenging aspects emerged: stabilising the trolley.
The next step was to choose a suitable control system. Since humans can adapt to the
movement of other humans, climb the stairs, and resist perturbations of other humans, the
human inspired control theories have been investigated.
Based on the literature search the risk-aware control was the most promising one. In case
of risk-aware control a value function is provided to the system, by which it can avoid the
undesirable states. By using a value function it does not require the calculation of exact
trajectories and therefore, it becomes computationally more efficient, than the other human
inspired control methods. In addition it learns and adjusts its control parameters by which
it can adapt to different situations.
In order to test its efficacy, it was implemented and tested in a simulation of the Pull-E,
where a planar projection of the tri-wheeled actuated trolley was dynamically simulated.
Force inputs could act on the trolley by using the mouse, as well as pre-determined sinusoids
acting on its centre of mass. The simulation showed the risk-aware control method already
resulted in instabilities when no perturbations affected the system. So far, the risk-aware control method was tested only for zero order systems. Therefore an adaptation of the riskaware
control method was made to allow the 2nd order system, by including angular velocities
in the state and modifying the value function. This control method is able to balance the
assistive trolley for forces that cause lower angular perturbations than 15 degrees.
In the future this control method needs to be improved to become more robust against
perturbation. The prototype needs to be rebuilt with stronger motors, and the control system
needs to be tested on the prototype. Finally, this prototype will be evaluated when human is
in the loop.
To conclude, Pull-E can facilitate elderly’s longer independence, but still a lot of work needs
to be done before it becomes a viable product.

Haptic steering guidance is an advanced driving assistance system which provides guidance torques on the steering wheel to assist a human driver. Improvements in performance, safety margins and workload have been reported for lane-keeping and curve negotiation tasks. On the other hand, the guidance system instigates increased driver torques, indicating the occurrence of a mismatch between driver and automation intention. A novel, criticality-based control structure was developed, capable of adapting to different driving conditions by using safety margins (operationalized as time-to-line crossing, TLC) as input. Twenty-four participants drove through a single-lane, 10.8 km long road, with as independent variables the road width (normal road width of 3 m, wide road width of 5 m) and the type of guidance received: no guidance (manual), haptic steering guidance based on lateral deviation from the center-line (performance-based guidance, PBG) and criticality-based guidance (CBG). On the normal road, results show similar benefits for both guidance systems compared to manual control, in terms of performance and safety margins. Workload was reduced by PBG, but both guidance systems yielded increased driver torques. On the wide road, participants drove closer to the center-line with PBG, but at the cost of significantly more guidance torques than CBG. Interestingly, this reduction in lateral deviation did not result in a significant improvement for lowest safety margins encountered. No subjective preference was found for either feedback condition. It can be concluded that criticality-based guidance is capable of adjusting to different driving conditions, without compromising safety margins, whilst greatly reducing guidance torques in situations where they are unneeded.