Bruce J. P. Mortimer

Vibrotactile transduction and transducers

The bodys sense of touch is potentially a versatile channel for the conveyance of directional, spatial, command, and timing information. Most practical implementations of vibrotactile systems require compact, light-weight actuators that can be mounted against the body. Eccentric mass motors are widely used for this application, yet their output is limited and the effects of loading on the transducers due to the skin and mounting arrangement have been largely ignored. Conventional linear actuators are well suited as vibrotactile transducers and can provide high output, but are typically limited to laboratory research due to their large size and cost. The effect of loading on various practical vibrotactile transducers is investigated using a skin impedance phantom and measuring the transducer displacement with respect to additional mass loading. Depending on the transducer design, loading can dramatically reduce the vibratory displacement and, in the case of eccentric mass motors, also increase the operating frequency. In contrast, a new linear actuator design can be designed to be almost independent of skin loading, by considering the mechanical impedance of the load and optimizing the transducer contact area.

Tactile Cuing to Augment Multisensory Human–Machine Interaction.

Tactile displays promise to improve the information-processing capacity of operators, especially when used in conjunction with visual and auditory displays. In this article, we describe current applications and future directions in tactile cuing.

Identifying Errors in Tactile Displays and Best Practice Usage Guidelines

Wearable tactile cueing provides a significant opportunity for performance and safety improvement during human-in-the-loop tasks. However, wearable technology and the human factors associated with tactile cueing presents specific challenges and many pathways for potential errors. This paper reviews tactile cueing displays, usage characteristics and identifies potential error pathways. We use a model for tactile salience to describe adaptive cueing and case-specific examples of potential errors. We propose that tactile designers work towards intelligent systems that recognize user responses, adapt the tactile signal characteristics and close the loop between the display and the task.

Information transfer within human robot teams: Multimodal attention management in human-robot interaction

Human-robot teams can incorporate advanced technology such as distributed mobile sensor networks, integrated communications, visualization technology, and other means to acquire and assess information. These factors can greatly affect mission effectiveness, safety, and survivability, by providing critical information and suggesting courses of action. However, information overload can result. Tactical situation awareness (SA) can be improved if human-robot communications are prioritized according to importance and appropriateness for single or multi-sensory display. In this paradigm, the tasks of the human and robot are somewhat independent or autonomous, but complimentary. Handling the amount, frequency and transfer of information, from the robot to the user requires a careful systems approach, an understanding of the mission context, and multisensory information processing issues. This report highlights attention management issues identified during task reengagement and offers guidelines relevant to tactile cues within multisensory bidirectional human robot communications.

Development of dual tactor capability for a soldier multisensory navigation and communication system

Development of new multisensory Soldier display systems requires context-driven evaluation of technology by expert users to assure generalizability to operations. The capture of Soldier performance demands is particularly challenging in this regard, as many factors converge to impact performance in actual usage. In this paper, we describe new capabilities for tactile communications that include an authoring system, use of android-driven displays for control and map-based information, and engineering tactors with differing salient characteristics. This allows development of a dual-tactor display that affords a larger variety of tactile patterns for communications, or TActions. These innovations are integrated in a prototype system. We used the system to present navigational signals to combat-experienced soldiers to guide development of tactile principles and the system itself. Feedback was positive for the concept, operational relevance, and for ease of interpretation.

Development of a planar shear sensor

This paper describes a wearable sensor that simultaneously measures both shear and orthogonal force. The planar shear sensor is based on inductive coupling between a small target and a series of adjacent coils. Lateral movement of the target changes the coupling between a primary coil and a series of geometrically shaped and scaled sense coils. Design of the sensor and methods for calibration are investigated. The wearable sensor can be used for measurement of in-situ foot loading during ambulation and we postulate that this may be useful for biomechanical analysis including exoskeletons and balance rehabilitation applications.

Multimodal Feedback for Balance Rehabilitation

This paper describes development of an activity based, multimodal balance rehabilitation training device. Various sensors can be used, including a force plate, inertial sensors, and depth sensing cameras, and various combinations of visual, auditory and tactile feedback can be configured depending on the rehabilitation task and activity. Tactile feedback is presented via a lightweight belt that is worn on the torso. Generally, visual feedback is only needed at the start of rehabilitation training (task orientation) while tactile feedback may be used to augment balance control. Tactile feedback can be configured as a cue that certain movement targets or limits have been reached or as an immediate indicator of the variance in postural sway. Tactile feedback allows the subject to naturally concentrate on the functional rehabilitation task, and is less reliant on visual or verbal cues.

Assessment of Wearable Tactile System: Perception, Learning, and Recall.

Previous research investigated concepts of tactile salience and core variables mediating effects on human perception and learning, resulting in validation of independent scaled ratings of tactile salience. This approach provides an integrated and systematic approach to assess effectiveness of tactile displays. We report an initial series of comparative tests of various multi-tactor cues, or tactions. Tactions were developed to vary in temporal sequencing and amplitude. In the first experiment 8 tactions were used; a follow-up investigation used 12. In this report we summarize results, with a focus on experiment methods association with measurement of tactile salience, ease of learning, and ease of recall.

Context Sensitive Tactile Displays for Bidirectional HRI Communications

Tactile displays have shown high potential to support critical communications, by relaying information, queries, and direction cues from the robot to the Soldier in a hands-free manner. Similarly, Soldiers can communicate to the robot through speech, gesture, or visual display. They could also respond to robot messages by pressing a button to acknowledge or request a repeat message. A series of studies have demonstrated the ability of Soldiers to interpret tactile direction and information cues during waypoint navigation in rough terrain, during day and night operations. The design of tactile display systems must result in reliable message detection. We have proposed a framework to ensure salience of the tactile cues. In this presentation we summarize research efforts that explore factors affecting the efficacy of tactile cues for bidirectional soldier-robot communications. We will propose methods for changing tactile salience based on the symbology and context.