Author details

Alexandru Forrai

Address all correspondence to: alexandru.forrai@tno.nl

TNO, Helmond, The Netherlands

#### References

• The moving armature is controlled between the two extreme positions, armature open and armature close, Δz<sup>0</sup> ¼ 10½ � mm (see Figure 12, right plot). In this case the main goal is to achieve so-called soft landing of the moving armature to reduce wear and noise. It is important to highlight that controller design is made based on the linearized plant, but validation of the controller in simulations or during hardware-in-the-loop (HIL) experiments

During our control design investigations, we considered that the armature position can be measured. In practice, there are applications, where the armature position cannot be measured

Therefore, we remark that controlling the moving armature without measuring the armature position (e.g., measuring only the current) remains a challenging research topic, which exceeds

shall be done using the nonlinear plant model.

Figure 12. System response with the gain-scheduled controller.

Figure 11. Gain and phase margin variation with z0.

102 Actuators

the goals and the limits of this chapter.

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**Section 3**

**Medical Applications**

**Medical Applications**

**Chapter 6**

**Provisional chapter**

**Quantitative Tactile Examination Using Shape Memory**

**Quantitative Tactile Examination Using Shape Memory** 

Diabetic neuropathy (DPN) is asymptomatic in its early phases but can cause serious complications as it progresses. Most DPN tests are cumbersome and produce only qualitative assessments, and simpler approaches that yield quantitative results are needed. Techniques that allow patients to perform examinations themselves would be especially valuable. In this study, we focused on quantifying the decline in tactile sensation associated with DPN and developed a measurement device that used a thin shape memory alloy (SMA) wire as the actuator. An ON/OFF pulse current caused the wire to shrink and expand. This vibration was amplified by a round-headed pin, allowing even DPN patients with reduced tactile sensitivity to detect the stimuli generated when lightly touching the pin with their fingertips. The tactile stimuli were ranked into 30 levels of intensity. A key advantage of the device is that it can be used by patients themselves, returning quantified results within minutes. Although developed for DPN, the method

**Keywords:** shape memory alloy actuator, neuropathy, tactile application, quantification,

In this chapter, we introduce a quantitative tactile examination device using shape memory actuators and discuss previous work by the authors on the use of such a system for the early

can be applied to the detection of peripheral neuropathy in general.

quantitative tactile examination, early detection

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.75084

**Alloy Actuators for the Early Detection of Diabetic**

**Alloy Actuators for the Early Detection of Diabetic** 

Junichi Danjo, Sonoko Danjo, Hideyuki Sawada,

Junichi Danjo, Sonoko Danjo, Hideyuki Sawada,

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Keiji Uchida and Yu Nakamura

Keiji Uchida and Yu Nakamura

http://dx.doi.org/10.5772/intechopen.75084

**Neuropathy**

**Abstract**

**1. Introduction**

**Neuropathy**

#### **Quantitative Tactile Examination Using Shape Memory Alloy Actuators for the Early Detection of Diabetic Neuropathy Quantitative Tactile Examination Using Shape Memory Alloy Actuators for the Early Detection of Diabetic Neuropathy**

DOI: 10.5772/intechopen.75084

Junichi Danjo, Sonoko Danjo, Hideyuki Sawada, Keiji Uchida and Yu Nakamura Junichi Danjo, Sonoko Danjo, Hideyuki Sawada, Keiji Uchida and Yu Nakamura

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.75084

#### **Abstract**

Diabetic neuropathy (DPN) is asymptomatic in its early phases but can cause serious complications as it progresses. Most DPN tests are cumbersome and produce only qualitative assessments, and simpler approaches that yield quantitative results are needed. Techniques that allow patients to perform examinations themselves would be especially valuable. In this study, we focused on quantifying the decline in tactile sensation associated with DPN and developed a measurement device that used a thin shape memory alloy (SMA) wire as the actuator. An ON/OFF pulse current caused the wire to shrink and expand. This vibration was amplified by a round-headed pin, allowing even DPN patients with reduced tactile sensitivity to detect the stimuli generated when lightly touching the pin with their fingertips. The tactile stimuli were ranked into 30 levels of intensity. A key advantage of the device is that it can be used by patients themselves, returning quantified results within minutes. Although developed for DPN, the method can be applied to the detection of peripheral neuropathy in general.

**Keywords:** shape memory alloy actuator, neuropathy, tactile application, quantification, quantitative tactile examination, early detection

#### **1. Introduction**

In this chapter, we introduce a quantitative tactile examination device using shape memory actuators and discuss previous work by the authors on the use of such a system for the early

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

detection of diabetic neuropathy (DPN) [1–3]. We consider the range of potential applications and the future potential of this technology.

A simple method for quantitative detection of the asymptomatic condition is therefore needed. By combining medicine and engineering, we developed a quantitative tactile examination device

Quantitative Tactile Examination Using Shape Memory Alloy Actuators for the Early Detection…

http://dx.doi.org/10.5772/intechopen.75084

111

The initial study targeted diabetes patients whose condition was associated with deterioration in sensation. The tactile sensation of diabetic patients was found to be lower than that of normal subjects [1, 2] and that of diabetic patients who were not conscious of the decline to be still lower [3].

The sense of touch relies on four main tactile receptors in the skin: the Meissner's corpuscle, Merkel disc, Ruffini ending, and Pacinian corpuscle. As shown in **Figure 1**, Merkel discs are located in the epidermis and are approximately 10 μm in diameter. They are used to sense pressure and texture. Meissner's corpuscles are primarily located immediately below the epidermis and are between 30 and 140 μm in length and 40–60 μm in diameter. They are used to sense stroking and fluttering. Ruffini endings are also located in the dermis, have a length of approximately 0.5–2 mm, and are used for the sense stretching of the skin. Pacini corpuscles are located in the subcutis and are approximately 0.5–2 mm in length and 0.7 mm in diameter. Based on their response speed and size, the receptors are given four labels: fast adapting I and

The receptors are present at different densities in different regions of the human body. **Figure 2** [13] shows the innervation density in the hand, which is where most human tactile recognition takes place. Receptors are particularly dense in the fingers and especially in the tips. Human fingers are therefore sensitive to a range of stimuli. The response of the receptors is closely related to nervous system activity, and the tips of the fingers are therefore also densely supplied with capillary vessels. When a diabetic condition restricts the blood flow in the capillary

based on detecting the decline in tactile sensation.

**2. Tactile sensation and diabetic neuropathy**

II (FA I and FA II) and slow adapting I and II (SA I and SA II).

**Figure 1.** Tactile receptors of the skin [3].

We have conducted a number of studies on tactile sense-presentation technology that applies micro-vibrations using thin shape memory alloys (SMA) [1–11]. The SMA allows for a compact device that consumes little power and causes no pain to patients.

Tactile-stimulus diagnostic techniques, such as the technique reported in this study, may be possible with other actuators such as small motors [12, 13], piezoelectric actuators [14], or pneumatic actuators [15]. However, each of these technologies requires large electromagnetic devices that require more power than that provided by a portable battery.

Piezoelectric actuators need a driving voltage of the order of several tens of volts, and their inclusion of mechanical parts makes their application in portable devices difficult [14].

Our tactile-stimulus presentation technology that uses a thin SMA avoids the problems of size and power consumption. The present iteration of the device can be driven with a small battery [2, 3, 5–7].

Quantitative diagnosis of DPN at present requires a machine costing at least several million yen and larger than 1 m on a side, such as nerve-conduction studies. Equipment for these tests, in addition to being cumbersome and expensive, requires skilled technicians for its operation.

Some patients refuse a second examination because nerve conduction studies and electromyography studies can be quite painful. Many asymptomatic diabetes patients are left untreated because of the cost, difficulty, and pain caused by the current methods for quantitative diagnosis of the neurological effects of diabetes.

In previous studies [1–3, 5–7], we have developed a range of simple, quantitative, and painless examination methods that use SMA, and the present study summarizes those studies and discusses future prospects.

A wide range of conditions contribute to hypoesthesia and/or peripheral nervous disorders, including the administration of anticancer drugs, DPN, vitamin deficiency, vasculitis, polyneuropathy, depression, alcohol dependence, infection, and uremia. However, the progress of the condition is generally slow, and most sufferers are initially unaware of its presence [16].

Peripheral neuropathy tests can be divided into two main types. The first is qualitative and includes the Achilles tendon reflex/vibration test. The second is nerve conduction studies (NCS), which involve complex and painful invasive examinations but provide quantified diagnoses. Both types require medical expertise and judgment and must be conducted by a healthcare professional. Patients have no access to their test results, making them less likely to seek treatment.

Approximately, half of all patients with diabetes contract asymptomatic neuropathy [17]. As the causes of neuropathy are not limited to diabetes mellitus, it is assumed that there are many more asymptomatic neuropathy sufferers. Currently, patients are unable to perceive the condition themselves, and no simple quantification scale is available. Even patients whose condition is treatable may be unaware of its presence and therefore fail to seek treatment.

A simple method for quantitative detection of the asymptomatic condition is therefore needed. By combining medicine and engineering, we developed a quantitative tactile examination device based on detecting the decline in tactile sensation.

The initial study targeted diabetes patients whose condition was associated with deterioration in sensation. The tactile sensation of diabetic patients was found to be lower than that of normal subjects [1, 2] and that of diabetic patients who were not conscious of the decline to be still lower [3].
