Figure 6.5. Cognitive pathways from tactor stimuli and handle position to derived spatial map

Figure 6.6. Major processing and control operations

6.4.6 Embedded Processing Control Requirements

The integration of the various signals and tactile transducers is achieved through a small embedded microprocessor. The processor also deals with the duty cycle control of key sensors and actuators to maximise battery life. Major processing operations are illustrated in Figure 6.6.

6.5 Concept Phase and Engineering Prototype Phase Trials

Early development work aimed to produce a concept testing unit built with no consideration for portability, power supply considerations, or optimized electronic design. A configurable processor with a connectable link to a desktop computer allowed the embedded software to be changed easily in order to investigate a variety of designs and algorithms.

224 6 Mobility AT: The Batcane (UltraCane)

A user review was incorporated at this concept phase to determine the viability of the basic concept. Results were very encouraging; approximately 10 concept trial users were found to gain a basic and intuitive competence within 30 min, and were able to demonstrate clear improvement in mobility in a controlled indoor environment featuring simple obstacles. Video recordings taken by agreement with the trial volunteers provided an opportunity for the self-learning and exploration sessions to be evaluated later.

The detailed engineering and trial prototype, illustrated above in Figure 6.3, was developed and manufactured in quantity to permit simultaneous trials by volunteer users to evaluate the electronic guide cane. The trial took place over a two-month period in which each volunteer used the cane in their everyday life. Trials were carried out over a six-month staged programme with volunteers in the UK, Germany and the USA. Volunteers were asked to keep detailed records of each use on their medium of choice. Records were used to assess the type of usage and the level of confidence. Statistics for the tests are given in Table 6.1.

Table 6.2 provides a summary of the results and typical user comments. As summarised in the table, the positive indications at the concept stage were confirmed and consolidated through the extensive experience of the trial period.

A small number of specific technical improvements were commonly indicated by the trial volunteers. At the trial prototype design stage it was expected that users would prefer a foldable form of the electronic cane for increased convenience. This

Table 6.1. Trial format, subjects and reviewers

Trial format and period

1 month using (2) forward and upward tactors

1 month also using side-view (4) tactors

Volunteer trial subjects

27 Visually impaired volunteers (54 person-months) U.K., Canada, USA, Germany

Other reviewers and advisors

22 Orientation and mobility specialists

10 Market influencers

Table 6.2. Summary results and comments

73% – felt confident using within 1 week 53% – felt £360–£720 appropriate price range

Typical comments

“Keeps me constantly updated in a crowded area”

“Let me explore surroundings to a much wider degree” “Positive guidance ... gave confidence ...”

“Knew when detecting – it was true and precise” “Tells me things I wanted to know”

obvious feature was omitted in the trial form to reduce the design challenge and cost, and in order to concentrate attention upon novel aspects.

As expected practically all the trial volunteers pressed for the device to be foldable. A second improvement implied was the provision of short and longrange control, accompanied by changes to the forward transducer beam shape to more closely track the user’s expected corridor of motion.

6.6 Case Study in Commercialisation

Results from the large scale trial summarized above were used to inform the optimization of the design in several areas: the incorporation of a foldable cane; the addition of a shortand long-range (to allow use in confined and open areas respectively) and accompanying changes to the transducer beams.

The incorporation of a folding capability was relatively simple in one respect: all the active components were re-sited to the handle assembly. This enabled the use of a standard multi-section graphite cane. It also necessitated the re-design of the transducers to suit their new position. Following the trial and its indicated changes, the needs and features of Table 6.3 were identified as targets for a product design.

The first ‘Ultracane’ product has been designed to include these features. For simplicity it includes twin ultrasonic transducers providing major forward and overhead directional information. The included angle, between the handle and cane shaft, allows the forward view transducer to be angled sideways to ‘shoreline’ a wall or other adjacent feature.

Two forward view distance ranges are provided, a long-range for use in open spaces and a short range for use in more crowded areas such as busy streets. The range can be changed at anytime. The selector is combined with the on-off control in a push-pull fingertip slider control on the underside of the handle. The position of the control provides a tactile confirmation of the current selected mode to the user. Figure 6.7 illustrates the resulting handle design and its features.

Table 6.3. Major identified need and proposed features