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Acceptance and Usability of a Soft Robotic, Haptic Feedback Seat for Autonomy Level Transitions in Highly Automated Vehicles
Abstract
Fully autonomous vehicles, capable of completing entire end-to-end journeys without the interference of a human driver, will be one of the biggest transforming technologies of the next decades. As the journey towards fully autonomous vehicles progresses, there will be an increase in the number of highly automated vehicles on the roads, requiring the human driver to take back control in situations, which cannot be handled by the vehicle autonomously. These human-robot take-over requests can lead to safety risks, in particular in scenarios when the driver fails to understand the take-over request and, hence, lacks situational awareness. This paper presents the acceptance and usability assessment of a haptic feedback driver seat capable of informing the driver of a take-over request through static mechano-tactile haptic feedback. The seat is equipped with an embedded array of soft pneumatic actuators, that have been fully modelled and characterised. The evaluation process of the haptic feedback seat engaged 21 participants who experienced both auditory and haptic feedback from the seat in a number of simulation experiments within a driving simulator. The vehicular technology was assessed through well-established methods to understand the acceptance (usefulness and satisfaction) and usability of the haptic feedback driver seat.
... Peters et al. [5] developed a soft robotic seat equipped with 12 custom fiber-reinforced pneumatic actuators designed to provide haptic feedback for human intervention requests and situational awareness in highly automated vehicles. The authors describe the design and fabrication of the soft pneumatic actuator with fiber and fabric reinforcement to achieve an enhanced structural integrity. ...
Building haptic interfaces for human-in-the-loop applications is a profound scientific and technological challenge. It requires developing methods to intuitively channel sensorimotor information between afferent and efferent neural pathways of a human user and inputs and outputs of an external system. In such applications, artificial touch may serve as a virtual extension of the human body to a remote location (e.g., teleoperation) or it can create a perception that an external system is a part of the body (e.g., prosthetics).
... Petermeijer et al. [36] found that high-intensity, long-duration vibrations led to faster responses but emphasized balancing with user comfort. Peters et al. [37] showed that seat-based vibrations could communicate hazard direction, while Beruscha et al. [38] reported that steering wheel vibrations helped drivers react faster to lane departure warnings compared to visual-only alerts. Effectiveness of haptic alerts can vary based on age, tactile sensitivity, and cognitive processing speed. ...
Effective driver re-engagement is essential for the safe operation of automated driving systems (ADS), especially during takeover requests. This study examines the effects of alert intensity and driver engagement in non-driving related tasks on takeover performance in automated vehicles. Forty-one participants navigated simulated driving scenarios with various hazards and alert conditions, allowing analysis of response times, physiological responses, and subjective perceptions. The findings showed that higher-intensity alerts significantly reduced reaction times, leading to quicker driver takeovers. Interestingly, engagement in certain secondary tasks sometimes improved driver responsiveness, suggesting that moderate cognitive engagement may enhance alertness. Response times varied across different driving scenarios, indicating the influence of situational context on driver behavior. Physiological measures, including eye-tracking and heart rate monitoring, showed increased cognitive and physiological arousal during takeover events, particularly in response to stronger alerts. Participants reported higher confidence and satisfaction with high-intensity alerts, without reporting increased annoyance, indicating a preference for more assertive alert mechanisms. These outcomes highlight the critical role of adaptive alert mechanisms in ADS design, promoting for context-aware signaling and real-time driver state monitoring to improve takeover performance and ensure vehicular safety. The study suggests that future ADS should integrate dynamic alert systems capable of adjusting intensity based on situational urgency and driver engagement, thereby enhancing overall system reliability and user acceptance.
Numerous studies have indicated that the use of a closed-loop haptic feedback system, which offers various mechano-tactile stimuli patterns with different actuation methods, can improve the performance and grasp control of prosthetic hands. Purely mechanical-driven feedback approaches for various mechano-tactile stimuli patterns, however, have not been explored. In this paper, a multi-cavity fluidic haptic feedback system is introduced with details of design, fabrication, and validation. The multi-cavity haptic feedback system can detect the physical touch with direction at the fingertip sensor. The direction of the force is reflected in the form of pressure deviation in the multi-cavity fingertip sensor. The feedback actuator generates various mechano-tactile stimuli patterns according to the pressure deviation from the fingertip sensor. Hence, users can identify the force with direction according to the stimuli patterns. The haptic feedback system is validated through two experiments. The initial experiment characterises the system and establishes the relationship between the fingertip sensor and feedback actuator. The subsequent experiment, a human interaction test, confirms the system's capability to detect force with directions and generate corresponding tactile stimuli in the feedback actuator. The outcomes corroborate the idea that participants are generally capable of discerning changes in angle.
Car seats represent a constructive - functional system including a variety of elements, assembled on a specific frame, among those the main components are the seat pan, the seat backrest, and the seat headrest. In order to improve the comfort of the driver and passengers, as well vehicle general safety, the car seats are under of intensive research and implementation of advanced developments.Thus, through of variety of sensors integrated into the seat, some important parameters are analysed for keeping the drivers alert and comfortable while driving semi-autonomous or autonomous cars. For adjustment of the seat linear and angular positions, a special system has been implemented, comprising electric, electronic, and pneumatic elements. Also, seat micro-adjustments are possible through the action of specific actuators. The car seat design and manufacture take into consideration a diverse array of data, based on a large range of parameters to face the diversity of drivers requirements. The present paper is advancing a conceptual development of car complex seat, integrating a number of active elements, with multiple possible adjustments. The new seat model is designed to satisfy a larger diversity of people both in terms of comfort and safety.
This final chapter, containing the full-length profiles of each of the 36 companies representing the base of this research project, plays an integral role in Masterpieces of Swiss Entrepreneurship. Although the various profiles have been quoted extensively as part of the analysis in the previous chapters, those excerpts were used to illustrate a particular concept, finding or practice. A reader, going through the previous chapters, cannot possibly gain a comprehensive understanding of the history and trajectory of a given company in the main book text; this section allows for a more in-depth reading, one company at a time. The company profiles are organized in the order of when each of the enterprises was founded.
Actuation means for soft robotic structures are manifold: despite actuation mechanisms such as tendon-driven manipulators or shape memory alloys, the majority of soft robotic actuators are fluidically actuated-either purely by positive or negative air pressure or by hydraulic actuation only. This paper presents the novel idea of employing hybrid fluidic-hydraulic and pneumatic-actuation for soft robotic systems. The concept and design of the hybrid actuation system as well as the fabrication of the soft actuator are presented: Polyvinyl Alcohol (PVA) foam is embedded inside a casted, reinforced silicone chamber. A hydraulic and pneumatic robotic syringe pump are connected to the base and top of the soft actuator. We found that a higher percentage of hydraulics resulted in a higher output force. Hydraulic actuation further is able to change displacements at a higher rate compared to pneumatic actuation. Changing between Hydraulic:Pneumatic (HP) ratios shows how stiffness properties of a soft actuator can be varied.
An important aspect in safety–critical domains is Situational Awareness (SA) where operators consolidate data into an understanding of the situation that needs to be updated dynamically as the situation changes over time. Among existing measures of SA, only physiological measures can assess the cognitive processes associated with SA in real-time. Some studies showed promise in detecting cognitive states associated with SA in complex tasks using brain signals (e.g. electroencephalogram/EEG). In this paper, an analytical methodology is proposed to identify EEG signatures associated with SA on various regions of the brain. A new data set from 32 participants completing the SA test in the PEBL is collected using a 32-channel dry-EEG headset. The proposed method is tested on the new data set and a correlation is identified between the frequency bands of β (12-30Hz) and γ (30-45Hz) and SA. Also, activation of neurons in the left and right hemisphere of the parietal and temporal lobe is observed. These regions are responsible for the visuo-spatial ability and memory and reasoning tasks. Among the presented results, the highest achieved accuracy on test data is 67%.
In conditional automation (level 3), human drivers can hand over the Driving Dynamic Task (DDT) to the Automated Driving System (ADS) and only be ready to resume control in emergency situations, allowing them to be engaged in non-driving related tasks (NDRT) whilst the vehicle operates within its Operational Design Domain (ODD). Outside the ODD, a safe transition process from the ADS engaged mode to manual driving should be initiated by the system through the issue of an appropriate Take Over Request (TOR). In this case, the driver’s state plays a fundamental role, as a low attention level might increase driver reaction time to take over control of the vehicle. This paper summarizes and analyzes previously published works in the field of conditional automation and the TOR process. It introduces the topic in the appropriate context describing as well a variety of concerns that are associated with the TOR. It also provides theoretical foundations on implemented designs, and report on concrete examples that are targeted towards designers and the general public. Moreover, it compiles guidelines and standards related to automation in driving and highlights the research gaps that need to be addressed in future research, discussing also approaches and limitations and providing conclusions.
Purpose
Humans are required to respond to a vehicle’s request to take-over anytime even when they are not responsible for monitoring driving environments in automated driving, e.g., a SAE level-3 vehicle. Thus, a safe and effective delivery of a take-over request from an automated vehicle to a human is critical for the successful commercialization of automated vehicles.
Methods
In the current study, a set of human-in-the-loop experiments was conducted to compare diverse warning combinations by applying visual, auditory, and haptic modalities under systematically classified take-over request scenarios in conditionally automated driving. Forty-one volunteers consisting of 16 females and 25 males participated in the study. Vehicle and human data on response to take-over request were collected in two take-over scenarios, i.e., a disabled vehicle on the road ahead and a highway exit.
Results
Visual-auditory-haptic modal combination showed the best performance in both human behavioral and physiological data and visual-auditory warning in vehicle data. Visual-auditory-haptic warning combination showed the best performance when considering all performance indices. Meanwhile, visual-only warning, which is considered as a basic modality in manual driving, performed the worst in the conditionally automated driving situation.
Conclusions
These findings imply that the warning design in automated vehicles must be clearly differentiated from that of conventional manual driving vehicles. Future work shall include a follow-up experiment to verify the study results and compare more diverse multimodal combinations.
Automated driving systems (ADSs) promise a safe, comfortable and efficient driving experience. However, fatalities involving vehicles equipped with ADSs are on the rise. The full potential of ADSs cannot be realized unless the robustness of state-of-the-art is improved further. This paper discusses unsolved problems and surveys the technical aspect of automated driving. Studies regarding present challenges, highlevel system architectures, emerging methodologies and core functions including localization, mapping, perception, planning, and human machine interfaces, were thoroughly reviewed. Furthermore, many stateof- the-art algorithms were implemented and compared on our own platform in a real-world driving setting. The paper concludes with an overview of available datasets and tools for ADS development.
For a successful market introduction of Level 3 Automated Driving Systems (L3 ADS), a careful evaluation of human–machine interfaces (HMIs) is necessary. User preference has often focused on usability, user experience, acceptance and trust. However, a thorough evaluation of measures when applied to ADS HMIs is missing. We investigated the appropriateness of nine self-reported measures in terms of reliability and validity. A sample of N = 57 participants completed two 15-min simulator drives with a L3 ADS. They experienced two variations of a HMI that differed in the degree of complying with common guidelines. Consistency analysis identified scales that showed insufficient reliability. Validity examination revealed a three-factorial structure of self-reports for construct validity. These factors are design-orientation, usability-orientation and acceptance-orientation. All measures were sensitive to the HMI manipulation and therefore exhibited criterion-related validity. The present study provides researchers and practitioners in the area of ADS with a recommendation for self-report measure application.
An unprecedented proliferation of autonomous driving technologies has been observed in recent years, resulting in the emergence of reliable and safe transportation services. In the foreseeable future, millions of autonomous cars will communicate with each other and become prevalent in smart cities. Thus, scalable, robust, secure, fault-tolerant, and interoperable technologies are required to support such a plethora of autonomous cars. In this article, we investigate, highlight, and report premier research advances made in autonomous driving by devising a taxonomy. A few indispensable requirements for successful deployment of autonomous cars are enumerated and discussed. Furthermore, we discover and present recent synergies and prominent case studies on autonomous driving. Finally, several imperative open research challenges are identified and discussed as future research directions.
Our review addresses one of the most used, but debated, topics in Ergonomics: Situation Awareness (SA). We examine and elaborate upon key SA models. These models are divided into individual SA, team SA and systems SA categories. Despite, or perhaps because of, the debates surrounding SA it remains an enduring theme for research and practice in the domain of Ergonomics, now for over two decades. A contingent approach, which seeks to match different models of SA to different types of ergonomics problem, enables the differences between positions to be revealed and reconciled, and the practitioner guided towards optimum methodological solutions.
Practitioner Summary
Measuring situation awareness (SA) in individuals, teams and systems has become a key objective in Ergonomics. One single approach to SA does not fit all problems encountered. This review shows the importance of considering all three types of models and achieving a match between them and the problem at hand.
The driver of a conditionally automated car is not required to permanently monitor the outside environment, but needs to take over control whenever the automation issues a “request to intervene” (i.e., take-over request). If the driver misses the take-over request or does not respond in a timely and correct manner, a takeover could result in a safety-critical scenario. Traditionally, warnings in vehicles are conveyed by visual and auditory displays, though recently it has been argued that vibrotactile stimuli could also be a viable approach to present a take-over request to the driver.
In this paper, we present a vibrotactile seat designed to convey dynamic vibration patterns to the driver. The seat incorporates 48 vibration motors (eccentric mass rotation) that can be individually controlled. One 6x4 matrix, with an average in-ter-motor distance of approximately 4 cm, is located in the seat back and one in the seat bottom. The DC-voltage to the motors is controlled by three Pulse Width Modulation (PWM) drivers, which in turn are controlled by an Arduino micro-controller.
A study with 12 participants was conducted to investigate (1) at which vibration intensity participants find a vibratory stimulus annoying and whether this thresh-old changes over time, (2) how well participants are able to discriminate vibratory stimuli as a function of spatial separation, and (3) which of six dynamic vibration patterns are regarded as most satisfying.
Results showed that participants’ annoyance threshold reduced when they were repeatedly exposed to vibrotactile stimuli. Second, the percentage of correct re-sponses in the two-point discrimination test increased significantly with increas-ing inter-stimuli distance (i.e., from 4 to 20 cm). Third, participants seemed to be more satisfied when more motors were activated simultaneously (i.e., more spatial overlap).
Overall, the results suggest that participants are well able to perceive vibrotactile in the driver seat. However, the results suggest that repetitive exposure to vi-brotactile stimuli may evoke annoyance, a finding that should be taken into ac-count in future designs of vibrotactile displays. Future studies should investigate the possibility to convey complex messages via the vibration seat.
This paper presents a first evaluation of multimodal language-based warnings for handovers of control in autonomous cars. A set of possible handover situations varying in urgency is described. A set of multimodal, language-based warnings for these situations is then introduced. All combinations of audio, tactile and visual warnings for handovers were evaluated in terms of perceived urgency, annoyance and alerting effectiveness. Results showed clear recognition of the warning urgency in this new context, as well as low perceived annoyance overall, and higher perceived effectiveness for critical warnings. The time of transition from self-driving to manual mode in the presence of the warnings was then evaluated. Results showed quicker transitions for highly urgent warnings and poor driving performance for unimodal visual warnings. These results provide a novel set of guidelines for an effective transition of control between car and driver in an autonomous vehicle.
Drivers' situation awareness is known to be remarkably low in the automated driving mode, which can result in a delayed and inefficient response when requested to resume control of the vehicle. The present study examined the usefulness of a haptic seat that projects spatial information on approaching vehicles to facilitate drivers' preparedness to take control of the vehicle. The results of a simulator study on 26 participants using behavioral and eye tracking techniques showed that when required to regain control, having haptic seat led to faster reactions in scenarios requiring lane changing. The haptic seat also reduced the probability that the participants would slow down below acceptable speeds on a freeway. Eye tracking showed that drivers had a more systematic scan of the environment in the first two seconds following the transition of control with a haptic seat. Overall, these findings suggest that the haptic seat can play a significant role in keeping drivers aware of surrounding traffic during automated driving, and consequently facilitate the control transitions between the vehicle and the driver.
Navigation systems usually require visual or auditory attention. Providing the user with haptic cues could potentially decrease cognitive demand in navigation. This study is investigating the use of haptic eyeglasses in navigation. We conducted an experiment comparing directional haptic cues to visual cueing in a car navigation task. Participants (N=12) drove the Lane Change Test simulator with visual text cues, haptic cues given by the eyeglasses and haptic cues given by a car seat. The participants were asked to confirm the recognition of a directional cue (left or right) by pressing an arrow on a tablet screen and by navigating to the corresponding lane. Reaction times and errors were measured. The participants filled in the NASA-TLX questionnaire and were also interviewed about the different cues. The results showed that in comparison to the visual text cues the haptic cues were reacted to significantly faster. Haptic cueing was also evaluated as less frustrating than visual cueing. The haptic eyeglasses fared slightly, although not significantly, better than the haptic seat in subjective and objective evaluations. The paper suggests that haptic eyeglasses can decrease cognitive demand in navigation and have many possible applications.
Tactile displays hold promise as an effective and efficient means of presenting a wide range of information to the driver. This study examined the subjective perceptions of urgency and annoyance for tactile signals of different pulse duration, interpulse interval (IPI), and pulse pattern from devices called tactors located on the wrist, on the waist belt, or in the seat pan. Results revealed significant utility (steep increases in urgency without similarly steep increases in annoyance) for signals presented in pulse durations from 10 to 150 ms with decreasing utility beyond this range (200 ms or greater). Perceived urgency showed a decreasing trend as the IPI increased. Strikingly similar magnitude estimation functions were obtained across the three tactor locations. Results are discussed in terms of their implications for tactile display design in vehicles.
Soft fluidic actuators consisting of elastomeric matrices with embedded flexible materials are of particular interest to the robotics community because they are affordable and can be easily customized to a given application. However, the significant potential of such actuators is currently limited as their design has typically been based on intuition. In this paper, the principle of operation of these actuators is comprehensively analyzed and described through experimentally validated quasi-static analytical and finite-element method models for bending in free space and force generation when in contact with an object. This study provides a set of systematic design rules to help the robotics community create soft actuators by understanding how these vary their outputs as a function of input pressure for a number of geometrical parameters. Additionally, the proposed analytical model is implemented in a controller demonstrating its ability to convert pressure information to bending angle in real time. Such an understanding of soft multimaterial actuators will allow future design concepts to be rapidly iterated and their performance predicted, thus enabling new and innovative applications that produce more complex motions to be explored.
Unlabelled:
The transmissibility of seat depends on the dynamics of both the seat and the human body, and shows how the amplification and attenuation of vibration varies with the frequency of vibration. A systematic methodology was developed for finite element (FE) modelling of the dynamic interaction between a seat and the human body and predicting the transmissibility of a seat. A seat model was developed to improve computational efficiency before models of the seat pan and backrest were calibrated separately using load-deflection and dynamic stiffness measurements, joined to form the complete seat model, and integrated with the model of a manikin for further calibration. The calibrated seat model was combined with a human body model to predict the transmissibility of the seat. By combining a calibrated seat model with a calibrated human body model, and defining appropriate contacts between the two models, the vibration transmissibility with a seat-occupant system can be predicted.
Practitioner summary:
FE models are capable of reflecting complex dynamic characteristics of a seat–body system. A methodology for using FE methods to model a seat–body system to predict seat transmissibility has been demonstrated. The method can be developed to explore how seating dynamics interact with human biodynamics.
Usability does not exist in any absolute sense; it can only be defined with reference to particular contexts. This, in turn, means that there are no absolute measures of usability, since, if the usability of an artefact is defined by the context in which that artefact is used, measures of usability must of necessity be defined by that context too. Despite this, there is a need for broad general measures which can be used to compare usability across a range of contexts. In addition, there is a need for "quick and dirty" methods to allow low cost assessments of usability in industrial systems evaluation. This chapter describes the System Usability Scale (SUS) a reliable, low-cost usability scale that can be used for global assessments of systems usability.
As technology advances, more functions have been, and continue to be added to the vehicle, resulting in increased needs for improved user interfaces. In this paper, we investigate the feasibility of using vibrotactile feedback for in-vehicle information delivery. First, we measured the spectral characteristics of ambient vibrations in a vehicle, and designed clearly distinguishable sinusoidal vibrations. We further selected via dissimilarity rating the four sets of sinusoidal vibrations which had three to six vibrations. Second, we evaluated the learnability of the vibration sets when associated with common menu items of a Driver Information System (DIS). We also replaced the two most confused sinusoidal vibrations with patterned messages, and assessed the degree of learnability improvement. Finally, we evaluated the extent to which participants could select a desired function in a DIS via vibrotactile messages while simultaneously performing a driving-like primary task with higher priority. The results demonstrated high potential for vibrotactile messages to be effectively used for the communicative transfer of in-vehicle system information.
This tutorial focuses on the sense of touch within the context of a fully active human observer. It is intended for graduate students and researchers outside the discipline who seek an introduction to the rapidly evolving field of human haptics. The tutorial begins with a review of peripheral sensory receptors in skin, muscles, tendons, and joints. We then describe an extensive body of research on "what" and "where" channels, the former dealing with haptic perception of objects, surfaces, and their properties, and the latter with perception of spatial layout on the skin and in external space relative to the perceiver. We conclude with a brief discussion of other significant issues in the field, including vision-touch interactions, affective touch, neural plasticity, and applications.
Soft material robotics is a rather young research field in the robotics and material science communities. A popular design is the soft pneumatic actuator (SPA) which, if connected serially, becomes a highly compliant manipulator. This high compliance makes it possible to adapt to the environment and in the future might be very useful for manipulation tasks in narrow and wound environments. A central topic is the modelling of the manipulators. While comparatively rigid continuum robots are build of metal or other materials, that conduct a linear behaviour, the material used in soft material robotics often exhibits a nonlinear stress-strain relationship. In this paper we contribute an identification method for material parameters and data-based approach within the constitutive equations of a Cosserat rod model. We target bending and extension stiffness, consider shear and neglect torsional strains. The proposed method is applicable to any continuum robot which can be modelled by the classic theory of special Cosserat rods, including constraint models, and shows great improvement in experimental results with mean position errors of 0.59% reference length.
Advanced driver assistance systems can effectively support drivers but can also induce unwanted effects in behavior. The present study investigates this adverse behavioral adaptation in adaptive Forward Collision Warning (FCW) systems. Other than conventional FCW systems that provide warnings based on static Time-To-Collision (TTC) thresholds, adaptive FCW systems consider the driver’s need for support by adjusting warning thresholds according to distraction. A neglected question is how drivers adapt their behavior when they use adaptive FCW systems under realistic conditions, i.e., when warnings occur infrequently but system functionality is anticipated. Forty-eight participants drove with two different FCW systems (adaptive vs. non-adaptive) while working on a secondary in-vehicle task in a driving simulator. During the main part of the experiment, no brake events occurred and hence FCW functioning was largely anticipated. Additionally, visual system feedback about the driver’s distraction state was manipulated between groups. Participants had significantly shorter minimal time-headways and TTCs when driving with the adaptive relative to the non-adaptive system. Participants with system feedback about distraction state spent generally more time with engaging in the secondary task. These results indicate behavioral adaptation which, however, is restricted to the task that is specifically supported by the system, namely longitudinal control.
Highly-automated driving requires drivers to take over the control of their vehicle in any situation. In takeover situations with short time budgets, a fast takeover is crucial. Here, drivers could be supported by an appropriate takeover request. This paper presents a driving simulator study investigating whether less critical takeover situations and a match between the urgency of a takeover request and the criticality of the takeover situation benefits drivers regarding their takeover performance and subjective experience. Fifty-two participants experienced two takeover situations with varying time budgets (short and long). A low urgent, visual-tactile takeover-request was presented to half of the participants. The other half experienced a highly urgent, visual-tactile takeover request, resulting in two conditions, in which the takeover requests matched the criticality of the takeover situation, and in two conditions, in which the takeover requests did not match. The results showed that participants generally performed better in low critical takeover situations, but they took over quicker in highly critical situations. However, a match neither shortens takeover time nor enhances subjective experience.
Conditionally automated driving (CAD) systems are expected to improve traffic safety. Whenever the CAD
system exceeds its limit of operation, designers of the system need to ensure a safe and timely enough transition from automated to manual mode. An existing visual Human-Machine Interface (HMI) was supplemented by different auditory outputs. The present work compares the effects of different auditory outputs in form of (1) a generic warning tone and (2) additional semantic speech output on driver behavior for the announcement of an upcoming take-over request (TOR). We expect the information carried by means of speech output to lead to faster reactions and better subjective evaluations by the drivers compared to generic auditory output. To test this assumption, N = 17 drivers completed two simulator drives, once with a generic warning tone (‘Generic’) and once with additional speech output (‘Speech +generic’), while they were working on a non-driving related task (NDRT; i.e., reading a magazine). Each drive incorporated one transition from automated to manual mode when yellow secondary lanes emerged. Different reaction time measures, relevant for the take-over process, were assessed. Furthermore, drivers evaluated the complete HMI regarding usefulness, ease of use and perceived visual workload just after experiencing the take-over. They gave comparative ratings on usability and acceptance at the end of the experiment. Results revealed that reaction times, reflecting information processing time (i.e., hands on the steering wheel, termination of NDRT), were shorter for ‘Speech +generic’ compared to ‘Generic’ while reaction time, reflecting allocation of attention (i.e., first glance ahead), did not show this difference. Subjective ratings were in favor of the system with additional speech output.
Vibrotactile stimuli can be effective as warning signals, but their effectiveness as directional take-over
requests in automated driving is yet unknown. This study aimed to investigate the correct response rate,
reaction times, and eye and head orientation for static versus dynamic directional take-over requests
presented via vibrating motors in the driver seat. In a driving simulator, eighteen participants performed
three sessions: 1) a session involving no driving (Baseline), 2) driving a highly automated car without
additional task (HAD), and 3) driving a highly automated car while performing a mentally demanding
task (N-Back). Per session, participants received four directional static (in the left or right part of the
seat) and four dynamic (moving from one side towards the opposite left or right of the seat) take-over
requests via two 6 × 4 motor matrices embedded in the seat back and bottom. In the Baseline condition,
participants reported whether the cue was left or right, and in the HAD and N-Back conditions participants
had to change lanes to the left or to the right according to the directional cue. The correct response rate
was operationalized as the accuracy of the self-reported direction (Baseline session) and the accuracy of
the lane change direction (HAD & N-Back sessions). The results showed that the correct response rate
ranged between 94% for static patterns in the Baseline session and 74% for dynamic patterns in the NBack
session, although these effects were not statistically significant. Steering wheel touch and steering
input reaction times were approximately 200 ms faster for static patterns than for dynamic ones. Eye
tracking results revealed a correspondence between head/eye-gaze direction and lane change direction,
and showed that head and eye-gaze movements where initiated faster for static vibrations than for
dynamic ones. In conclusion, vibrotactile stimuli presented via the driver seat are effective as warnings,
but their effectiveness as directional take-over requests may be limited. The present study may encourage
further investigation into how to get drivers safely back into the loop.
The task of car driving is automated to an ever greater extent. In the foreseeable future, drivers will no longer be required to touch the steering wheel and pedals and could engage in non-driving tasks such as working or resting. Vibrotactile displays have the potential to grab the attention of the driver when the automation reaches its functional limits and the driver has to take over control. The aim of the present literature survey is to outline the key physiological and psychophysical aspects of vibrotactile sensation and to provide recommendations and relevant research questions regarding the use of vibrotactile displays for taking over control from an automated vehicle. Results showed that a distinction can be made between four dimensions for coding vibrotactile information (amplitude, frequency, timing, and location), each of which can be static or dynamic. There is a consensus that frequency and amplitude are less suitable for coding information than location and timing. Vibrotactile stimuli have been shown to be effective as simple warnings. However, vibrations can evoke annoyance, and providing vibrations in close spatial–temporal proximity might cause a lack of comprehension of the signal. We describe the sequential stages of a take-over process and argue that vibrotactile displays are a promising candidate for redirecting the attention of a distracted driver. Furthermore, vibrotactile displays hold potential for supporting cognitive processing and action selection while resuming control of an automated vehicle. Finally, we argue that multimodal feedback should be used to assist the driver in the take-over process.
A simple, two-constant, constitutive relation, applicable over the entire renge of strains, is proposed for rubber networks. Behavior in simple extension is derived as an axample.
Highly automated driving allows the driver to temporarily turn away from the driving task, meaning he or she does not have to monitor the system. This leads to the challenge of getting the driver back into the loop, if the automation reaches a system boundary. This study investigates, whether augmented reality information can positively influence the take over process. Therefore we evaluated two augmented reality concepts. The concept “AR red” displays a corridor on the road to be avoided by the driver in a take over scenario. The concept “AR green” suggests a corridor the driver can safely steer through. Results indicate that the type of augmented reality information does not influence take over times, but considerably affects reaction type. Visual inspection revealed higher consistency in driving trajectories for participants following the proposed corridor of “AR green” concept as compared to trajectories of drivers confronted with the restricted zone of “AR red”.
In this paper, we present the design of a low-cost haptic actuator called a pactor that is capable of delivering tactile stimuli eliciting varying levels of attention capture. The pactor design consists of a crankshaft mechanism attached to an RC servo that produces a linear displacement at the endpoint. It can apply a 0-2.0cm displacement to the human body at a variety of actuation rates. We conducted a study to measure the displacement detection threshold for the pactors, and their perceived level of attention capture and urgency. In our study with 25 participants we found that actuation speed was the most significant factor affecting detection threshold. We also observed that the level of attention capture was dependent on both actuation speed and stimulus intensity. We propose that dynamic range of actuation speed and stimulus magnitude are important design parameters that enable actuators to achieve variable attention capture (VAC). This in turn will allow actuators to provide better opportunities to present information at an appropriate level of attentional salience.
Most haptic feedback devices to date are designed to be alerts or warnings that capture a user's attention. This can be disruptive or annoying when the user needs to focus on another task of higher importance. We believe that haptic feedback that elicits positive affect can manage attention capture across a wider spectrum than feedback with negative affect. In this study, we explore the affective response to several haptic actuator designs for better management of user attention. We evaluate six parameters that may impact affect: stimulus location on the body, actuation type, actuation intensity, actuation profile, actuator material and actuator geometry. A total of 30 subjects participated in this study (average age 24±3 years). Of the six parameters, we found that actuation profile had the most significant impact on affect. We also found that devices with negative affect were better able to capture the user's attention. Due to the variability in the verbalized preferences among subjects, we propose outfitting all haptic actuators with an intensity control. We anticipate that the results of this study will guide designers in modifying key parameters of haptic devices to appropriately manage user attention.
Previous research demonstrated that a haptic driver seat can effectively convey information to drivers, and suggests that it may be an ideal method for presenting haptic information because it maintains contact with the driver. The current study progresses this research by investigating whether a haptic seat can be used as the sole method for communicating multiple and meaningfully different alerts such that drivers quickly execute the correct response maneuver. An intuitive manner for presenting up to seven haptic alerts through the driver seat was developed based on driver performance with an earlier haptic seat design. Twenty-four drivers then participated in an on-road study that, through three experiments, investigated: (1) whether driver response performance to the alerts degrades as the number of possible alerts (one, three, or seven alerts) is increased, (2) whether driver response performance to the alerts degrades when alerts are presented through the same seat location, and (3) whether the haptic seat can effectively alert distracted drivers to a surprise barricade. In Experiment 1, despite drivers always making the correct response maneuver, their manual response time and verbal response accuracy significantly degraded as the number of alerts increased from three to seven. In Experiment 2, drivers’ manual response time significantly improved when alerts were presented through unique seat locations. In Experiment 3, distracted drivers that received an alert returned their gaze to the forward roadway sooner, lifted their foot up from the throttle sooner, and pressed the brake pedal sooner than distracted drivers that did not receive an alert. Overall, the study shows that confusion and delayed responses may occur when the number of possible alerts is increased, but that the information transmitted by the haptic seat alerts can be secured if the alerts are presented through unique seat locations that are spaced far apart, and map to the desired manual response. In balancing the tradeoff between communicating a multitude of information to drivers and minimizing performance decrements, a haptic seat that conveys three alerts is recommended when quick and accurate manual responses are required and additional alert modalities are not utilized. These findings are expected to inform the design of haptic driver seats.
The perceptual overloads of visually and auditorily based information and their interference phenomena within vehicles led to research for the applicability of haptically based information and the haptic interfaces to intelligent vehicles. Because seats are the interface that touches the largest area of the driver's body, the driver's seat in vehicles has been the focus of a promising haptic interface that can improve the safety of drivers and the effectiveness and efficiency of the information transfer between vehicles and drivers. This study aims to provide practical guidelines as a building block for designing the haptic (or vibrotactile) interface in a vehicle's driver's seat by investigating, through four experiments, 1) proper intensity of vibration, 2) minimum distance of spatially distinguishable vibrations, 3) proper position and direction of vibration, and 4) proper rhythm of vibration. Twenty participants took part in the experiments, which were conducted in driving simulation environments. These environments consisted of a real car seat, commercial vibration actuators (i.e., the eccentric motors), and a monitor that showed scenes of the road while driving. This study recommended the proper intensity (approximately 26 to 34 Hz and 2.0 to 3.4 G), position (seat pan or back support), direction (horizontal or indirect), intervibration distance (8 to 9 cm), and rhythm of vibration (3-s duration with 0.5-s interval), and showed how the characteristics of drivers, such as gender and age, had effects on setting the design variables of the haptic interface in the vehicle seat. © 2010 Wiley Periodicals, Inc.
The System Usability Scale (SUS) is an inexpensive, yet effective tool for assessing the usability of a product, including Web sites, cell phones, interactive voice response systems, TV applications, and more. It provides an easy-to-understand score from 0 (negative) to 100 (positive). While a 100-point scale is intuitive in many respects and allows for relative judgments, information describing how the numeric score translates into an absolute judgment of usability is not known. To help answer that question, a seven-point adjective-anchored Likert scale was added as an eleventh question to nearly 1,000 SUS surveys. Results show that the Likert scale scores correlate extremely well with the SUS scores (r=0.822). The addition of the adjective rating scale to the SUS may help practitioners interpret individual SUS scores and aid in explaining the results to non-human factors professionals.
There is no standard way of measuring driver acceptance of new technology. A review of the literature shows that there are almost as many methods of assessment of acceptance as there are acceptance studies. The tool for studying acceptance of new technological equipment that is presented here has a major advantage compared with many other studies in that esoteric knowledge of scaling techniques is not required. The technique is simple and consists of nine 5-point rating-scale items. These items load on two scales, a scale denoting the usefulness of the system, and a scale designating satisfaction. The technique has been applied in six different studies in different test environments and analyses performed over these studies show that it is a reliable instrument for the assessment of acceptance of new technology. The technique was sensitive to differences in opinion to specific aspects of in-vehicle systems, as well as to differences in opinion between driver groups. In a concluding section explicit recommendations for use of the scale are given.
The implementation of haptic interfaces in vehicles has important safety and flexibility implications for lessening visual and auditory overload during driving. The present study aims to design and evaluate haptic interfaces with vehicle seats. We conducted three experiments by testing a haptic seat in a simulator with a total of 20 participants. The first experiment measured reaction time, subjective satisfaction, and subject workloads of the haptic, visual, and auditory displays for the four signals primarily used by vehicle navigation systems. The second experiment measured reaction time, subjective satisfaction, and subjective workloads of the haptic, auditory, and multimodal (haptic + auditory) displays for the ringing signal used by in-vehicle Bluetooth hands-free systems. The third experiment measured drivers' subjective awareness, urgency, usefulness, and disturbance levels at various vibration intensities and positions for a haptic warning signal used by a driver drowsiness warning system. The results indicated that haptic seat interfaces performed better than visual and auditory interfaces, but the unfamiliarity of the haptic interface caused a lower subjective satisfaction for some criteria. Generally, participants showed high subjective satisfaction levels and low subjective workloads toward haptic seat interfaces. This study provided guidance for implementing haptic seat interfaces, and identified the possible benefits of their use. We expect to improve safety and the interaction between driver and vehicle through haptic seats implemented in vehicles.
Taxonomy and definitions for terms related to on-road motor vehicle automated driving systems
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The effects of takeover request modalities on highly automated car control transitions
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Cadillac Active Safety -Safety Alert Seat
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- Automotive
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- Bhosale
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- Rodday