Sensory testing device

Abstract

A system for providing calibrated stimulus delivery, comprising an actuator configured to generate vibration stimuli to a patient’s skin or body portion via a test pad. An accelerometer 115 measures a

Description

Field of the Invention The present invention relates to a sensory testing device, and more particularly to a sensory testing device capable of providing mechanical stimuli with optional temperature control and recording vibration sensory detection. Background to the Invention The ability to detect transient, oscillating, low intensity mechanical stimuli is an important evolutionarily-conserved sensory ability that is thought to be protective against insect bites and associated pathogens like malaria. This vibration detection is achieved through specific classes of rapidly conducting sensory nerves that have specialised endings in the skin. A range of diseases (like diabetes) and treatments (such as cancer chemotherapy) cause damage to nerves, resulting in neuropathy that leads to numbness, poor co-ordination, risk of consequent tissue damage and also persistent pain. This sensory loss is often insidious and detected late when there is no chance to treat it. As a result, the nerve damage and symptoms can be permanent. This sensory function is normally tested clinically using the application of a tuning fork to a bony prominence. The level of vibration at a set frequency that can be detected is measured. However, this method of testing is not practical for home use as it requires skill, independent observations and a trained operator. A number of haptic devices have been developed that can provide an equivalent vibration stimulus to the skin. However, they often require complicated equipment, a trained operator and skill to use and interpret the results. As a consequence they have not been widely adopted clinically and are not used in the community. This is because the delivered stimulus is highly-dependant on a range of factors which are difficult to control. For current methods of delivering mechanical vibration stimuli, there is significant variability inherent in the testing which is due to patient-specific, researcher-specific and environmental factors. These sum to make such methods inherently unreliable and impractical to use unless performed by an expert in a clinical environment or controlled lab setting. Thermal testing currently utilizes feedback calibration and is an accepted gold standard in sensory testing but the equivalent feedback calibration and control has not been done for mechanical vibration stimuli. In order to reliably deliver the same vibratory stimulus regardless of environmental factors, skin temperature, tissue compliance, device orientation etc., the delivered stimulus needs to be precisely measured and then compensated accordingly. It is an aim of the present invention to overcome, or at least mitigate, disadvantages of existing methods of vibration stimuli testing. Summary of the Invention Accordingly, a first aspect of the invention provides a device fortesting vibration detection, comprising a test pad for contact with skin of a body portion, an actuator configured to generate vibration stimuli that are delivered to the body portion via the test pad, an accelerometer configured to measure an amplitude of vibration generated by the actuator, a controller configured to control the actuator using actuator drive parameters, and a processor configured to: instruct the controller to control the actuator to provide a calibration stimulus according to one or more initial actuator drive parameters, receive, from the accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters, determine one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein the one or more final test actuator drive parameters are predicted to provide one or more target amplitudes, instruct the controller to control the actuator to provide a test vibration stimulus according to the one or more final test drive parameters, receive user input indicating that a test stimulus is sensed by a user, and receive, from the accelerometer, the amplitude of the test stimulus sensed by the user. Preferably, one or more initial actuator drive parameters and the one or more final test actuator drive parameters comprise one or more actuator drive values, wherein each drive value is operable for a predetermined time period. Optionally, each of the one or more final test actuator drive parameters comprise one or more sequential final test actuator drive values which sequentially increase or decrease to increase or decrease the amplitude of displacement of the actuator. Each sequential final test actuator drive value may be configured to provide a target amplitude for a predetermined time period. Preferably, the processor is configured to generate a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values. The device may further comprise a thermoelectric element configured to heat or cool the skin in contact with the test pad, a thermometer arranged to measure the temperature of the skin in contact with the test pad, wherein the controller is preferably further configured to control operation of the thermoelectric element and receive temperature data from the thermometer. Optionally, the processor is configured to instruct the controller to operate the thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature fora predetermined period of time. The processor may be configured to instruct the controller to operate the thermoelectric element according to one or more drive values, wherein the one or more drive values control the thermoelectric element to achieve one or more temperature values. The one or more drive values may sequentially increase or decrease the thermoelectric output to increase or decrease the temperature of skin from a first predetermined temperature or to a second predetermined temperature. The processor may be further configured to receive user input indicating that a change in temperature is sensed by a user. The device preferably further comprising means for temporary attachment to a portion of human skin. According to a second aspect of the invention, there is provided a method for controlling a device for providing mechanical stimuli, the method comprising controlling an actuator to provide a calibration stimulus to a portion of skin according to one or more initial actuator drive parameters, receiving, from an accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters, determining, by a processor, one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein the one or more final test actuator drive parameters are predicted to provide one or more target amplitudes, controlling the actuator to provide a test vibration stimulus according to the one or more final test drive parameters, receiving, by the processor, user input indicating that a test stimulus is sensed by a user, receiving, from the accelerometer, the amplitude of the test stimulus sensed by the user, and storing the amplitude of the test stimulus sensed. Preferably, the step of determining one or more final-test actuator drive parameters comprises generating a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values. The method preferably further comprises controlling a thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature fora predetermined period of time. Optionally, the thermoelectric element is controlled according to one or more thermoelectric drive values, wherein the one or more thermoelectric drive values control the thermoelectric element to achieve one or more temperature values. The method may comprise sequentially increasing or decreasing the thermoelectric output according to the one or more thermoelectric drive values to increase or decrease the temperature of skin from a first predetermined temperature to a second predetermined temperature. Preferably the processor is further configured to receive user input indicating that a change in temperature is sensed by a user. According to a third aspect of the invention, there is provided a system for providing calibrated stimulus delivery, comprising: an actuator configured to generate vibration stimuli to a body portion, an accelerometer configured to measure an amplitude of vibration generated by the actuator, a controller configured to control the actuator using actuator drive parameters, and a processor configured to: instruct the controller to control the actuator to provide a calibration stimulus according to one or more initial actuator drive parameters, receive, from the accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters, determine one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein the one or more final test actuator drive parameters are predicted to provide one or more target amplitudes, instruct the controller to control the actuator to provide a test vibration stimulus according to the one or more final test drive parameters. Preferably, the one or more initial actuator drive parameters and the one or more final test actuator drive parameters comprise one or more actuator drive values, wherein each drive value is operable for a predetermined time period. Each of the one or more final test actuator drive parameters may comprise one or more sequential final test actuator drive values which sequentially increase to increase the amplitude of displacement of the actuator. Each sequential final test actuator drive value is optionally configured to provide a target amplitude for a predetermined time period. The processor is preferably configured to generate a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values. The system preferably further comprises a thermoelectric element configured to heat or cool the skin in contact with the test pad, a thermometer arranged to measure the temperature of the skin in contact with the test pad, and wherein the controller is further configured to control operation of the thermoelectric element, and receive temperature data from the thermometer. The processor is optionally configured to instruct the controller to operate the thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature fora predetermined period of time. The processor may be configured to instruct the controller to operate the thermoelectric element according to one or more drive values, wherein the one or more drive values control the thermoelectric element to achieve one or more temperature values. The one or more drive values may sequentially increase or decrease the thermoelectric output to increase or decrease the temperature of skin from a first predetermined temperature or to a second predetermined temperature. The invention provides a simple to use, self-calibrating haptic device to test vibration detection, with optional thermal control capability, that can be used either in a clinical or in a non-clinical setting, as described herein. The present invention thus facilitates early detection and diagnosis of sensory loss (for example, during chemotherapy treatment). Delivery of calibrated vibration stimuli to the body surface according to the invention allows reliable measurement of vibration detection thresholds in humans taking account of the variation in properties of the underlying tissues (including temperature and compliance) and the means of attachment. The invention enables the reliable delivery of precise mechanical stimuli under a range of different conditions, thereby allowing the home use of vibration sensation testing applied to different subjects, with different geometries and body compositions on multiple occasions over time. On each occasion the vibration amplitude and preferably skin temperature can be adjusted so that the same stimulus pattern is delivered to the nerves in the tissues under comparable conditions so the response can be referenced against the actual stimulus parameters with increased precision. The invention provides feedback calibration of the delivered vibration stimulus. The calibration routine reduces the variance in stimuli delivered in both bench models and in tests on healthy human subjects. It also improves the precision with which the subject's vibration detection threshold is determined overtime with repeated rounds of testing. The invention also concerns a method for improving the reliability of quantitative assessment of vibration sensation in human subjects that could be undertaken at a variety of body sites and under a range of different environmental locations including the home. The optional additional ability to control skin temperature at the site of stimulus delivery provides an additional means to reduce variance. Brief description of the Figures Figure 1 is an exploded schematic diagram of the internal components of a sensory testing device according to an embodiment of the invention; Figure 2a is a top view of a sensory testing device according to an embodiment of the invention; Figure 2b is a schematic rear-side view of a sensory testing device according to an embodiment of the invention; Figure 3 is a schematic diagram illustrating functional relationships between components of a sensory testing device according to an embodiment of the invention; Figure 4 is a flow diagram of a method of calibrating a sensory testing device according to an embodiment of the invention; Figure 5 is a graphical representation of target stimulus profile as an average of individual non-calibrated probe stimuli; Figure 6 is a schematic diagram illustrating a testing protocol according to an embodiment of the invention; Figure 7 is a graphical representation of displacement against drive steps for calibrated and non-calibrated stimuli; Figure 8 is a graphical representation of threshold variance for calibrated and noncalibrated testing; Figure 9 is a graph illustrating the effect of controlled skin temperature on vibration detection thresholds; and Figure 10 is a is a chart illustrating the effect of controlled skin temperature on threshold variance. Detailed Description Sensory testing device Referring briefly to figure 2a, a sensory testing device 200 comprises housing 201, test pad 202 on which the area being tested can be placed (e.g., tip of the finger, the palm), screen 207 and response buttons 205, 206, as will be described in more detail below. Figure 2b shows power switch 206 and power socket 204 on rear face of device 200. In an alternative embodiment, power to device 200 can be provided by batteries. Figure 1 shows internal components housed within sensory testing device 200: temperature sensor 110, thermal faceplate 111 (which together provide the test pad of Figure 2a), safety temperature sensor 112, thermoelectric element 113, stack top plate 114, accelerometer 115, heatsink 116, haptic bracket 117, haptic actuator 118, stack cradle 119, cradle spring 120 and pressure sensor 121. Device 200 also comprises processing and controller circuitry (not shown). It will be appreciated that the components of device 200 are connected and in communication with each other as necessary to facilitate data flow and instruction, the details of which are well known in the art. In an alternative embodiment, the haptic actuator, thermoelectric element, pressure sensor and temperature sensor form a peripheral device which can be affixed to a desired region of the body, such that the components are connected, via a wired connection or wireless communications, to a controller and processor housed in a separate housing. Haptic actuator 118 may be a linear resonant actuator (LRA) haptic device or an eccentric rotational mass (ERM) haptic device or another suitable actuator used to deliver vibrational stimulation. LRA haptic devices are preferred over ERM haptic devices, as LRA haptic devices can be driven at varying amplitudes at well-defined frequencies (and it is generally not possible to decouple frequency and amplitude using ERM devices). Accelerometer 115 measures the extent of mechanical vibration generated by haptic actuator 118 and so provides data necessary to characterize the delivered stimulus and adjust it accordingly, as will be described below. In alternative embodiments, component 115 may be a spatial displacement sensor to provide information about the stimulus and the basis of adjustment. An accelerometer is sufficiently compact to allow for a breadth of design options (size, orientation etc.) for the device and therefore the range of different body sites / regions to test. Figure 3 shows the information and data flow relationships between various internal components of device 200. Controller 308 is responsible for driving haptic actuator 118 to provide mechanical / vibrational stimulation via haptic drive circuitry 312 and reading accelerometer data at >400Hz (for adjustment to the drive value of the actuator 118 to achieve target amplitude). Pressure sensor 121 measures whether adequate contact between the device and body. Controller 308 is preferably an Arduino ESP32. Controller 307 is responsible for closed-loop control of thermoelectric element 113 to maintain a target temperature (when selected), measured by temperature sensor 110. The closed-loop control of the temperature utilises temperature sensor 111 to monitor element temperature using thermal measurement circuitry 309. Closed-loop control uses a PID (proportional integral derivative) algorithm to maintain temperature within 0.1°C of set value (for example, 32 °C), by driving a current sink to power the thermoelectric element 113. Thermoelectric element 113 is preferably a Peltier element and is controlled by thermal drive circuitry 310. In one embodiment, a further temperature sensor 111 is provided which functions, alongside thermal safety circuitry 311, to provide independent temperature measurement to ensure thermoelectric element 113 does not exceed a set temperature. Controller 307 is preferably an Arduino MKRZero or indeed any microcontroller with SPI and I2C capabilities, and with an on-board DAC of preferably 10-bit resolution or greater. Processor 306 is in communication with controllers 307 and 308 and outputs to user interface 203 to elicit user instruction and to issue instructions to initiate temperature stabilization, initiate the calibration routine, adjust the vibration stimulus profile, reads signals and data from the and perform calibration computations (e.g. regression fit and prediction, as described below). Processor 306 comprises or is in communication with memory (not shown in Figure 1) to store detection thresholds and any other data depending on use-case (e.g., all accelerometer data during a session, adjusted drive values, starting temperature etc). User interface response buttons 204, 205 facilitate user input when vibration / change in temperature is detected. Processor 306 may be any sufficiently powered processing unit, for example, a Raspberry Pi or similar. The coding language is preferably Python due to its numerous libraries for signal processing, statistics, data management, although any suitable coding language could be used. In use, an appropriate body site is placed in contact with test pad / stack top plate 114 for assessment of sensory function. Skin temperature control is optional; the decision to control stimulated skin area temperature is made prior to initiating the vibration testing. Skin temperature is known to influence the sensitivity of nerves in the skin to vibration. If temperature control is chosen, then a closed-loop feedback system controls thermoelectric element 113 to heat / cool the contact area to the desired temperature (typically to normal skin temperature 30-32°C) and maintain it within a predefined range, as will be described further below. Temperature control could alternatively be achieved via various hardware configurations particularly if heating alone is sufficient using resistive devices. For example, cooling capability could be provided by an active circulated mechanism. Any temperature dependant probe and amplification circuitry could be used. Temperature sensor 110 is preferably a PtlOOO resistance thermometer due to its high accuracy and small footprint. A thermistor ora thermode may be used instead in an alternative embodiment. Calibration Before each new test, the vibration stimulus is calibrated. The calibration routine builds a model relating actuator drive values to a target set of vibration amplitudes. The calibrated stimulus parameter set (actuator drive values) is then input to the circuitry of the haptic actuator to deliver target vibration amplitudes and thereby reliably deliver vibration stimuli to the body site. The calibration process is repeated for each new test site and after change in contact or measurement condition. An initial calibration routine is described with reference to Figure 4, which begins at step 401. If temperature control is chosen (step 402), a closed-loop thermal control routine is performed, as per steps 409, 410 and 411 in order to achieve and maintain a predetermined skin temperature at the test site. If temperature control is not chosen, vibration calibration is initiated (step 403). A calibration stimulus is applied (step 404), measured (step 405) and compared to target stimulus (406). Drive adjustments to the calibration stimulus are computed at step 407 before testing begins (step 408). More specifically, a calibration stimulus envelope is delivered through the device in contact with the subject's skin. The calibration stimulus envelope is discretized into a plurality of sequential time periods of a fixed duration so as to provide constant vibration stimulus (having a sinusoidal waveform of a specified frequency and amplitude) during each time period. At the end of each time period the vibration intensity (defined as the amplitude of acceleration / displacement) of the actuator is altered. For example, a predetermined percentage amplitude increase may be applied to calibration stimulus after each time period if it is an ascending ramp stimulus. During each time period, accelerometer 115 measures motion of haptic actuator 118. The accelerometer data is processed (e.g. filtering, integration to compute velocity / displacement). The extent of processing is dependent on how the target was set and the stimulus intensity was defined (e.g. acceleration). Processor 306 applies a bivariate linear regression model to fit the applied drive values of the actuator to the acceleration / displacement measured by accelerometer 115 at each time period. The number of data pairs on which the regression model is built depends on the number of time-steps (discrete stimulus intensity steps). The regression model is used to generate a series of drive values which are predicted to correspond to acceleration amplitudes of a target acceleration profile. In this instance, the target acceleration amplitudes are predetermined empirically by initiating a large number of non-calibrated stimuli at the desired body location across multiple participants. The acceleration amplitudes (or displacement amplitudes) are averaged across these stimuli which determines the target profile. Figure 5 illustrates a target profile (dotted line) among multiple non-calibrated profiles. While time is presented as continuous in Figure 5, in reality the stimulus is discretized and the average (median) acceleration amplitude (or displacement amplitude) is computed at each discreet step / time period. The target stimulus / acceleration amplitude profile may be generated differently, for example via different empirical determination, a theoretically driven set of values, or an arbitrary target. An empirical approach is preferred because it produces target profiles which require the calibration to adjust the drive values the least. Otherwise, the adjustments may have to be unreasonably large to hit target profiles. These adjustments may be outside limits set either through software, or more importantly, hardware limits of the chosen haptic actuator. The fit of actuator displacement to actuator drive values may be computed via other computational functions or statistical models, curve fitting or even via machine learning algorithms. Linear regression is the current preferred option because the relationship between input drive value and acceleration output of the haptic actuator is linear with a high proportion of shared variance (>90%) making linear regression precise while remaining computationally efficient. For any adopted method, the discretization of the stimulus needs to result in a sufficient number of data points to viably fit drive value to stimulus intensity. An alternative method of calibration uses a continuous, smooth calibration stimulus intensity change. This would also provide abundant data for fitting drive values to acceleration. However, the nature (discretized vs continuous) of the calibration stimulus should match test stimuli delivered during testing sessions after calibration. Otherwise, discrepancies between the calibration stimulus used to determine drive value to acceleration fit and actual testing stimuli may impact negatively, rather than positively, on testing reliability. The actuator drive value profile (i.e. the drive values to apply at each time period) generated by processor 306 according to the regression model provides acceleration amplitudes (or displacement) at each time-step which correspond to the target amplitudes. The regression model thereby provides predicted drive values for the haptic actuator which would elicit the target stimulus intensity profile for a particular test site and for a particular participant. It will also signal (as a fault condition to be remedied) if the coupling between the participant and the device is incorrect (e.g. too loose or too tight) such that the device is incapable of delivering the intended stimulus profile. Alternatively to the described preferred method, closed-loop calibration during the delivery of a vibration stimulus is also possible. Using the same or similar sensors described as part of device 200 - accelerometer 115 and pressure sensor 121 -allows for different approaches to on-line stimulus calibration. The described calibration methods can apply to a number of different stimulus envelopes - ascending and descending step-wise ramping stimulation, continuous ramping stimulation, single-step stimulation, and multiple site stimulation (as in two-point discrimination tasks) to accommodate the desired psychophysical method of measurement. Sensory testing Adjusted drive control values, as determined by the calibration process, are stored and provided by processor 306 to controller 308 which then provides them to drive circuitry 312 of haptic actuator 118 during detection threshold testing. If temperature control is required during the test session, temperature can be maintained as constant so that a temperature-controlled calibrated vibration stimulus can be delivered reliably. The main stages of sensory testing will be described with reference to Figure 6. At stage 1, the test pad of the device is applied to the skin (e.g. palm). Skin temperature can be measured by temperature sensor 110 and the skin heated / cooled using thermoelectric element 113 to establish a stable baseline under the device of 32°C. This baseline temperature can be maintained using a closed-loop feedback process. Vibration calibration occurs at stage 2. An initial vibration stimulus is applied by haptic actuator 118 at a target frequency (e.g. 128Hz). The amplitude of the calibration stimulus envelope of haptic actuator 118 at each time period is measured using accelerometer 115. Data gathered by accelerometer 115 is used as an input to an adjustment function (as per the calibration process) to define the actuator drive values for the subsequent testing stimulus envelope. Vibration detection threshold (VDT) testing is then started (stage 3). Four testing stimulus envelopes are delivered, each of which comprises a predetermined number of time periods and delivers a predetermined rate of rise of vibration amplitude. The preferred time period duration is 0.5-1.5 seconds to allow for a participant to respond as soon as they detect a vibration. Due to lag introduced by detection and response processing, discretizing the stimulus assures reliable determination of thresholds. Alternate time-step durations, or a continuous stimulus intensity alteration over time, or other more complex stimulus envelope profiles may be adopted depending on the application. For each testing stimulus envelope, the participant presses a response button 205 on device 200 to signal that they have detected the vibration. The minimum vibration amplitude detected by a patient is recorded and stored by processor 306. Crudely, the higher the vibration amplitude before detection, the greater the loss of innervation. A similar process is repeated for the warm and cold detection thresholds (WDT, CDT) (stages 4 and 5). The thermoelectric element warms or cools the skin at a set rate (e.g. l°C / s) and the subject / patient presses a button when they detect skin temperature changing. Similarly to the vibration testing, the temperature increase and decrease test is repeated four times with rest periods in-between where the temperature is adjusted back to 32°C. At the end of testing (stage 6) device 200 then enters a standby mode and the skin temperature returns to its previous resting state. An average of the minimum vibration amplitude detected is calculated, as well as an average of the warm and cool temperature detection thresholds. The key parameters are therefore temperature below 32°C at which cool is first detected, temperature above 32°C at which warm is first detected, and minimum amplitude at which vibration is detected. Figure 7 shows data from 160 calibrated and non-calibrated stimuli in 10 participants. It can be seen that calibrated stimuli (solid line) are tightly distributed around the target amplitude profile (dashed line) while non-calibrated stimuli (dotted line) show much more variance. Physically, the calibrated stimulus is more consistent and as such the delivered stimulus is consistent across measures and participants. Calibrated stimuli therefore have less between- and within- participant variance than non-calibrated (probe) stimuli. In Figure 7, the dashed line is a target set for the calibration to achieve. The remaining lines are the averages of 160 calibrated (solid line) and non-calibrated (dotted line) stimulus ramps across 10 participants with the whiskers indicating a 95% confidence interval. Figure 7 shows the effectiveness of the calibration routine to achieve target displacement with expected variance. The dotted line represents 160 uncalibrated ramps which drift off the target dashed line, and with much more variance. Calibration of vibration stimuli therefore delivers the expected stimulus envelope (the target) reliably (low variance between ramps). Figure 8 depicts data showing consistency of calibrated measurements when compared to non-calibrated measurements, at different times and under moderately different conditions, for the same 10 participants. The variance of non-calibrated threshold estimates is significantly higher (t(9) = 2.58, p = .029, d = 0.83 [0.08 - 1.521]). The reliability of how the stimulus is perceived increases with calibration, which is important when tracking differences overtime (e.g., during the course of chemotherapy treatment). A participant's report of their detection thresholds for calibrated stimuli is therefore shown to be consistent when compared to thresholds obtained from non-calibrated stimuli. Vibration detection thresholds (the amplitude at which participants can first detect the device vibrate) may be computed as an average across a number of ramps (most commonly 3). However, if those ramps significantly vary, the average may be a poor representation of the actual threshold. As shown in Figure 8, variance decreases when ramps are calibrated. The variance for individual participants is also shown. Variance decreased when calibrated for 8 out of 10 participants. Calibration therefore has beneficial impact not only on the physical stimulus being delivered (as shown in figure 7) but also on the reliability of the perceived thresholds being measured. Figure 9 depicts the results of an experiment in which vibration detection thresholds were measured for 10 ramps in a row on the pulp of the index finger on the non-dominant hand at 1) fixed skin temperature of 32°C (solid line) and 2) non-fixed skin temperature (dashed line). The thresholds are considerably more stable across 10 ramps if the temperature is controlled. The between-participant variance is also much smaller. If only 3-4 ramps are conducted during a test and the average is calculated, there will likely be significant instability and variance of ramps if skin temperature is not controlled. Controlling skin temperature during vibration detection threshold measurement therefore has a significant impact. Figure 10 shows within-participant variance from the same experiment, and therefore the reliability of measuring the threshold for a participant. The experiment was run in separate sessions, 4 for each participant on different days. Variance is generally low when skin temperature is controlled and it is much less variable across participants. This is evidence for increased reliability of measuring thresholds when clamping skin temperature.

Claims

1. A device fortesting vibration detection, comprisinga test pad for contact with skin of a body portion,an actuator configured to generate vibration stimuli to the body portion via the test pad,an accelerometer configured to measure an amplitude of vibration generated by the actuator,a controller configured to control the actuator using actuator drive parameters, and a processor configured to:instruct the controller to control the actuator to provide a calibration stimulus according to one or more initial actuator drive parameters,receive, from the accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters,determine one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein the one or more final test actuator drive parameters are predicted to provide one or more target amplitudes, instruct the controller to control the actuator to provide a test vibration stimulus according to the one or more final test actuator drive parameters,receive user input indicating that a test stimulus is sensed by a user, and receive, from the accelerometer, the amplitude of the test stimulus sensed by the user.

2. The device of claim 1, wherein the one or more initial actuator drive parameters and the one or more final test actuator drive parameters comprise one or more actuator drive values, wherein each drive value is operable for a predetermined time period.

3. The device of claim 1 or 2, wherein each of the one or more final test actuator drive parameters comprise one or more sequential final test actuator drive values which sequentially increase or decrease to increase or decrease the amplitude of displacement of the actuator.

4. The device of claim 3 when dependent on claim 2, wherein each sequential final test actuator drive value is configured to provide a target amplitude for a predetermined time period.

5. The device of any preceding claim, wherein the processor is configured to generate a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values.

6. The device of any preceding claim, further comprisinga thermoelectric element configured to heat or cool the skin in contact with the test pad,a thermometer arranged to measure the temperature of the skin in contact with the test pad, andwherein the controller is further configured tocontrol operation of the thermoelectric element, and receive temperature data from the thermometer.

7. The device of claim 6, wherein the processor is configured to instruct the controller to operate the thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature for a predetermined period of time.

8. The device of claim 6, wherein the processor is configured to instruct the controller to operate the thermoelectric element according to one or more drive values, wherein the one or more drive values control the thermoelectric element to achieve one or more temperature values.

9. The device of claim 8, wherein the one or more drive values sequentially increase or decrease the thermoelectric output to increase or decrease the temperature of skin from a first predetermined temperature or to a second predetermined temperature.

10. The device of claim 9, wherein the processor is further configured to receive user input indicating that a change in temperature is sensed by a user.

11. The device of any preceding claim 1, further comprising means for temporary attachment to a portion of human skin.

12. A method for controlling a device for providing mechanical stimuli, the method comprisingcontrolling an actuator to provide a calibration stimulus to a portion of skin according to a one or more initial actuator drive parameters,receiving, from an accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters,determining, by a processor, one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein theone or more final test actuator drive parameters are predicted to provide one or more target amplitudes,controlling the actuator to provide a test vibration stimulus according to the one or more final test drive parameters,receiving, by the processor, user input indicating that a test stimulus is sensed by a user,receiving, from the accelerometer, the amplitude of the test stimulus sensed by the user, andstoring the amplitude of the test stimulus sensed.

13. The method of claim 12, wherein the step of determining one or more final-test actuator drive parameters comprises generating a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values.

14. The method of claim 12 or 13, further comprising controlling a thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature for a predetermined period of time.

15. The method of claim 14, further comprising controlling the thermoelectric element according to one or more thermoelectric drive values, wherein the one or more thermoelectric drive values control the thermoelectric element to achieve one or more temperature values.

16. The method of claim 15, further comprising sequentially increasing or decreasing the thermoelectric output according to the one or more thermoelectric drive values to increase or decrease the temperature of skin from a first predetermined temperature to a second predetermined temperature.

17. The method of claim 16, wherein the processor is further configured to receive user input indicating that a change in temperature is sensed by a user.

18. A computer-readable medium comprising executable instructions which, when executed by a processor, cause a computer to perform the method of any one of claims 12 to 17.

19. A system for providing calibrated stimulus delivery, comprising: an actuator configured to generate vibration stimuli to a body portion,an accelerometer configured to measure an amplitude of vibration generated by the actuator,a controller configured to control the actuator using actuator drive parameters, and a processor configured to:instruct the controller to control the actuator to provide a calibration stimulus according to one or more initial actuator drive parameters,receive, from the accelerometer, one or more calibration amplitude values corresponding to each of the one or more initial actuator drive parameters,determine one or more final test actuator drive parameters based on the one or more calibration amplitude values, wherein the one or more final actuator drive parameters are predicted to provide one or more target amplitudes,instruct the controller to control the actuator to provide a test vibration stimulus according to the one or more final test drive parameters.

20. The system of claim 19, wherein the one or more initial actuator drive parameters and the one or more final test actuator drive parameters comprise one or more actuator drive values, wherein each drive value is operable for a predetermined time period.

21. The system of claim 19 or 20, wherein each of the one or more final test actuator drive parameters comprise one or more sequential final test actuator drive values which sequentially increase to increase the amplitude of displacement of the actuator.

22. The system of claim 21 when dependent on claim 20, wherein each sequential final test actuator drive value is configured to provide a target amplitude for a predetermined time period.

23. The system of any of claims 19 to 22, wherein the processor is configured to generate a regression model using the one or more initial actuator drive parameters and the one or more calibration amplitude values.

24. The system of any of claims 19 to 23, further comprisinga thermoelectric element configured to heat or cool the skin in contact with the test pad,a thermometer arranged to measure the temperature of the skin in contact with the test pad, andwherein the controller is further configured tocontrol operation of the thermoelectric element, andreceive temperature data from the thermometer.

25. The system of claim 24, wherein the processor is configured to instruct the controller to operate the thermoelectric element according to closed-loop control using temperature data from the thermometer to achieve a predetermined skin temperature for a predetermined period of time.

26. The system of claim 24, wherein the processor is configured to instruct the controller to operate the thermoelectric element according to one or more drive values, wherein the one or more drive values control the thermoelectric element to achieve one or more temperature values.

27. The system of claim 26, wherein the one or more drive values sequentially increase or decrease the thermoelectric output to increase or decrease the temperature of skin from a first predetermined temperature or to a second predetermined temperature.19

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