BACKGROUND

Technological Field

The present invention relates to a signal processing device and a signal processing method.

Background Information

An expansion/contraction sensor that outputs a signal corresponding to expansion/contraction is known from the prior art. The expansion/contraction sensor comprises a measurement object (one example of an “object”) whose electrical resistance changes (one example of a “physical change”) with applied force. Thus, by measuring the electrical resistance of the measurement object, the expansion/contraction sensor can detect the expansion and contraction of the expansion/contraction sensor itself or the stress applied to the expansion/contraction sensor.

One example of such an expansion/contraction sensor is a CNT strain sensor that uses carbon nanotubes (hereinafter abbreviated as CNTs) as the measurement object (for example, refer to Japanese Laid-Open Patent Application No. 2013-104796 (Patent Document 1) or Japanese Laid-Open Patent Application No. 2015-147038 (Patent Document 2). A CNT has the property that the electrical resistance will change with applied force to the CNT. Thus, by measuring the electrical resistance of the CNTs provided in the CNT strain sensor, the expansion and contraction of the CNT strain sensor itself or the stress that is applied to the CNT strain sensor can be detected. In addition, another example of the expansion/contraction sensor is a braid-based sensor that employs a braid that expands and contracts using conductive fibers and rubber fibers as the measurement object, and that detects the amount of expansion and contraction of the braid by measuring the electrical resistance of the braid (refer to Shinya Namikawa and two others “Basic Investigation of Braid-Based Sensor Using Resistance Change in Response to Stretching,” Interaction 2016 (Non-Patent Document 1)). Other examples of strain sensors are disclosed in, for example, Japanese Laid-Open Patent Application No. 2016-136989 (Patent Document 3) and Japanese Patent No. 4422728 (Patent Document 4).

In an expansion/contraction sensor that outputs an output signal whose signal level corresponds to the electrical resistance of a measurement object, such as a CNT strain sensor or a braid-based sensor, the output signal of the expansion/contraction sensor tends to be asymmetric in terms of expansion and contraction of the expansion/contraction sensor. That the output signal is asymmetric means that either the rising of the output signal is slowed down with respect to the falling of the output signal or the falling of the output signal is slowed down with respect to the rising of the output signal. For example, in the case of an expansion/contraction sensor in which the output signal rises in response to the expansion of the expansion/contraction sensor and the output signal falls in response to the contraction of the expansion/contraction sensor, the falling of the output signal will be slowed down with respect to the rising of the output signal. The cause of the time lag is thought to be that, due to, for example, the viscoelasticity of the rubber fibers, etc., provided in the expansion/contraction sensor, the expansion/contraction sensor tends to deform more gradually when the expansion/contraction sensor contracts compared to when the expansion/contraction sensor expands. The expansion/contraction sensor is often used as a wearable sensor for measuring the motion of the wearer, but there is the problem that the ability to follow the movement of the wearer is not the same during expansion and as during contraction.

SUMMARY

The present disclosure is made in view of the problem described above, and one object thereof is to eliminate asymmetry from the output signal of a sensor whose output signal is asymmetric in terms of the rise time in response to a physical change and the fall time in response to a physical change that is the opposite of said physical change.

A signal processing method according to this disclosure comprises receiving a signal that rises in response to a physical change and falls in response to an opposite physical change that is opposite to the physical change from a sensor that outputs the signal, and correcting a signal lag as either a rising of a received signal that has been received from the sensor lags with respect to a falling of the received signal or the falling of the received signal lags with respect to the rising of the received signal.

A signal processing device according to this disclosure comprises a receiver configured to receive a signal that rises in response to a physical change and falls in response to an opposite physical change that is opposite to the physical change from a sensor that outputs the signal, and a signal processor configured to correct a signal lag as either a rising of a received signal received by the receiver lags with respect to a falling of the received signal or the falling of the received signal lags with respect to the rising of the received signal.

