Smart glove enables digital molding with manual correction
By Fred Holtkamp and Joost van Hoof
Abstract
For the manufacturing of individual aids and appliances the molding of the foot and the lower leg, as exact as possible, is an essential condition. In case of the plaster technology the tactile sense and the pressure used by the hands of the pedorthist or of the orthopedic technician when molding the plaster is decisive. A digital implementation of the tactile sense and the pressure of the pedorthist can be reached by scanning the body segments manually with a so-called smart glove.In the study presented here it is tested if a smart glove equipped with sensors is suitable as a digital tool that collects data concerning the position and the pressure of the hand of the expert and that supplies the basis for a virtual last. It turned out that a prototype of the smart glove is feasible and functional. The next step will be to improve the latest prototype so that sensors can be integrated directly in the glove.
Approximately one third of the European population deals with foot problems. These foot problems have a profound impact on one’s personal mobility. Worldwide, the percentage of people dealing with foot problems is much larger.
Prescribing an orthopaedic device such as a foot orthosis or an ankle foot orthosis (AFO) is the most convenient way to treat these disorders. The “human” sense of the podiatrist, the orthopaedic shoe technologist or ortho-thist in processing tactile information plays an important role.
Indeed, the pressure applied by the expert’s "own" hands” at the curing plaster provides important information, with respect to the amount of applied pressure or correction .
At present, manufacturing an orthosis or prosthesis involves an extensive process of making a model of the involved body parts from a plaster reproduction.Both the plaster of Paris reproduction and the cast model allow corrections to be made, corresponding to the body segments’ composition (for instance, the location of bony landmarks or soft tissue) determined by the deformation of body tissue.
This process has several disadvantages:
1. making a plaster reproduction is stressful for the client,
2. it is time-consuming, due to the time required for the model to dry, and
3. the corrections made to the model and the amount of pressure needed to assess body segments are implicit and subjective to the level of the practitioner’s experience.
Therefore, its shape and characteristics are hard to transfer onto colleagues for further production and processing (Figure 2). This practice-based, implicit way of working, can be made explicit, using the proprioception of the expert in a digital way when designing orthopaedic devices for clients.
The wish to digitally register data that is gathered during the measuring phase of the orthopedic process, had led to the emergence of various systems that are commercially available. CAD-CAM and scanning devices have many advantages, including the digital registration of all information from the start of the measuring phase such as modifications and adjustments. With the use of scanners and digitisers, one can gather 3D information, which can be processed using a computer. This information can then be sent to a computerized production machine.
Within the production chair of prosthetics and podiatry, these technologies are becoming widely accepted, whereas these technologies are emerging within the domains of orthotics and orthopaedic shoe technology. One of the conditions for general acceptance and introduction of CAD-CAM systems is that these systems should be user-friendly, less strenuous on the clients, and match the way of thinking and working of OT experts. One of the challenges is that the OT expert lacks the sense of touch when using digital systems.
This new approach using proprioception in the production of orthopaedic devices should be more client-friendly, more accurate, reproducible, transferrable, and accountable in comparison with traditional methods. In addition, it should facilitate experts in explicating knowledge within the field of orthopaedic technology and may subsequently be integrated in both vocational education and supplementary training for current practitioners.
Therefore, new technological solutions are needed to replace current analogue way of working, by introducing a technology that enables a direct digital reconstruction of body segments without the loss of feeling – tactile information - of the practitioner.
This can be accomplished by scanning the body segments manually with a so-called smart glove, in which position and pressure sensors are integrated that resemble data indicating the contours and composition of the body segments. This data is the input for a computer aided design (CAD) system.
Objective
The aim of the research was to define and design a digital tool to conduct data acquisition with respect to the position and the pressure applied by the orthotist during a casting process in a client-friendly and tactile manner. The experience and skills of the orthotist should be integrated in the use of the designed versatile measuring device, preferably in the form of the smart glove device .
Design process
The V-Model design method represents the various stages that are passed through during the software development life cycle, and it is was used for the design process of the smart glove. Originally developed for software engineering it can also be used for product development because it can be used also iteratively.
The model starts at the top-left stage and end at the top-right tip and defines the different stages. In collaboration with the proposed initial users of the smart glove, i.e., the orthotists, prosthetist and orthopaedic shoe technologists, we defined the objectives and the concepts of the application in respect of the functionality. For instance, what the glove should look like and what its functionalities should be. In turn, this was also the start to draw up the requirements of the future device.
The next stage consisted of defining the performance requirements, keeping in mind the operating environment, in more detail. A number of alternatives were visualised in a morphological chart and these variants were weighed with respect to the specifications and costs. The most promising alternative was elaborated into a proof of principle.
After tests, in total about 40 hours, conducted with students and colleagues, requirements for the sensors, embodiments of the glove, and choices of used materials were adapted in the first prototype. Simultaneously the data architecture and first software versions for handling the acquired data were designed and tested. These data should become available in the right form to use as input for the CAD system.
Results
A proof of principle of the future smart glove is operational. This glove has multiple pressure sensors on each of the five fingers and the palm of the hand. There is roughly one sensor for every phalanx. These FlexiForce sensors have a pressure range between 0 and 445 N/cm² with a resolution of 0.1 N/cm².
There are two types of FlexiForce sensors that are included in the prototype. Each of them have different sensing area sizes, namely type A201, which has a diameter of 9.53 mm, and type A401, which has a diameter of 24.4 mm. The smart glove prototype has a total of twenty-six pressure sensors (Figure 3): Eighteen type A201 sensors and eight type A401 sensors. Every segment of the hand (phalanx and palm), pressures are being measured, and the position of the fingers is registered.
When using the gloved hand in practice, data is being generated on the pressures and forces exerted by the OT expert on the body part of the client. In the former situation this was done during casting in an implicit fashion. The pressure sensors in the data glove fill a data register.
The glove itself is connected to a transmitter that is based on BlueTooth, which sends data to a computer system wirelessly and at given intervals. The forces and pressures are visualised on a separate computer screen using a dedicated software package, appearing as various shades and colours (Figure 4). For instance, blue indicates a low pressure, and red indicates the opposite, a high pressure. The image is more than just a visual representation of measurement data, it also helps to convey the information to other OT experts, and even physicians, the client him/herself, and the whole chain of professionals involved in the design and delivery of an orthotic device or an orthopaedic shoe.
The data can be used simultaneously to gain insight in the amount of pressure and force that are being exerted when corrections are being made by OT experts. The data set can be used to determine boundaries for maximum pressures that an AFO can exert on a certain body part, in order to prevent the development of skin defects that can develop into ulcerations or other wounds.
In addition to the pressure sensors, the prototype also includes three ascension position sensors operating based on a magnetic principle (the resolution of the sensor is one degree). This number will eventually increase to five or six position sensors in the final smart glove design. These positioning sensors, which generate X, Y and Z coordinates, are key elements in generating input for CAD model (Figure 5).
In this prototype, the position and pressure sensors are working as foreseen and the data string can be used as input for the CAD system (Figure 1). The position and pressure sensors used in the glove, together with the newly developed electronics to operate wirelessly as well as the developed test software made it possible to demonstrate the manipulation of the position and orientation and applied pressures of the smart glove.
All these data are needed in order to produce an accurate 3D model of a body part that is presented on a computer screen. This model can be used to make corrections by an OT expert. A final model can be used as the CAM-file (computer aided manufacturing), which can be used to steer a fraise or milling cutter, or even a rapid prototyping machine, which can turn the digital model into a tangible end product.
Conclusion
A prototype of the smart glove is operational. Next step in the design of the smart glove is to improve the current prototype more in the direction of smart textiles in order to integrate sensors into the glove. Also, the pre-processor of the CAD system needs to be developed in further detail.
Corresponding author
Ing. Fred Holtkamp M.Sc.
Associate Lector
Fontys University of
Allied health Professions
5600 AH, Eindhoven
Bibliography
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Aantal gebruikers 2009-2013, hulpmiddelencategorie C05 : Orthesen http://www.gipdatabank.nl/databank.asp.
2 F.C. Holtkamp (2002) CAD CAM in de orthopedie techniek. In: Geertzen, J. H. B., Rietman, J. S. (eds.), Amputatie en prothesiologie van de onderste extremiteit. Lemma, Utrecht. pp. 331-349.
3. F.C. Holtkamp, M.J. Verkerk, J. van Hoof, E.J.M. Wouters (2016) Mapping user activities and user environments during the client intake and examination phase: an exploratory study from the perspective of ankle foot orthosis users. Technology and Disability 28(4):145-157 doi: 10.3233/TAD-160452.
