JP2007195592A - Safety system for myoelectric interface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety system which includes a safety technology at the starting for preventing a system from starting operation when a user does not intend and for preventing the system from starting the operation by involuntary motions, when the user does not intend and a safety technology at the stopping for safely halting the operation, even if a switch can not be turned off because of entering noises and for bringing the operation to an emergency halt immediately before a collision against a wall, a fall into a step, or the like without turning off the myoelectric switch when the user panics. <P>SOLUTION: The operation starts by switching all of the myoelectric switches turned on when a signal intensity of myoelectricity exceeds a threshold value to an off-state after keeping the switched-on state for a prescribed period of time. A user device is operated by two or more myoelectric switches, and the operation of the user device is halted when all of the myoelectric switches are turned on. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for realizing safe start and stop in a myoelectric switch which is a kind of user interface (myoelectric interface) using myoelectricity.

  By detecting a muscle action potential (myoelectricity), for example, it is possible to operate a user device such as a prosthetic hand (myoelectric prosthetic hand) or an electric wheelchair. In order to operate the myoelectric prosthetic hand, basically, a myoelectric sensor is brought into contact with the skin surface, and a myoelectric signal is measured. Therefore, when each signal intensity exceeds a predetermined threshold value, a corresponding operation is selected. For example, in the case of a forearm myoelectric prosthesis, 2ch myoelectricity is measured by a sensor that is in contact with the surface of the extensor and flexor muscles remaining at the stump and the strength of the electromyogram measured on the flexor side exceeds the threshold The hand can be closed, and conversely, when the extensor side exceeds the threshold value, the hand can be opened.

  “Myoelectricity” is a kind of bioelectric potential observed during muscle contraction, and is observed as a surface myoelectric potential on the skin surface, for example. In this specification, the “myoelectric interface” is defined as a user interface that uses myoelectric to operate a tool or machine (user device) such as a prosthetic hand or an electric wheelchair, and the myoelectric interface As one type, a switch that is turned on when the myoelectric signal intensity exceeds a threshold is defined as a “myoelectric switch”. This myoelectric switch can be used as an alternative interface in the case where it is difficult to operate the push button switch due to muscle weakness or the like.

Such myoelectric switches have problems when starting and stopping. Since the myoelectric signal is a weak signal of about several μV to several mV at the time of starting, it is easily affected by disturbance noise such as a commercial power supply (100 V). When strong disturbance noise is mixed, there are cases where the switch is turned on when not intended. For this reason, it has been difficult to apply to a user interface such as a mobile device that may be accompanied by a serious danger due to malfunction.
In the switch type user interface, there are the following two methods for stopping the operation, but each has a problem.

(1) “Turn off the operation switch”:
In the case of myoelectric switches, there are cases where the switch cannot be turned off due to noise mixing, and there are cases where the switch cannot be turned off due to the force in an emergency (panic). Therefore, it is dangerous to use this method. Therefore, it is necessary to use a stop switch as in the following method.

(2) “Turn on the stop switch”:
However, for example, in a user interface for a handicapped person with limited motor functions, it may be difficult to add a stop switch.

The present invention solves such a problem, and as a safety technique at the time of starting, the system prevents the system from starting operation when it is not intended due to disturbance noise mixed into the myoelectric switch, and the involuntary movement It is intended to prevent the system from starting operation when not.
In addition, as a safety technique at the time of stopping, the present invention can safely stop the operation even if noise is mixed and the switch cannot be turned off, and without turning off the myoelectric switch at the time of panic, The purpose is to enable emergency stop immediately before a collision or just before falling to a step.

  In the safety system of the myoelectric interface for detecting myoelectricity and operating the user device according to the present invention, all the myoelectric switches that are turned on when the signal strength of the myoelectric signal exceeds the threshold value maintain the switch ON state for a predetermined time. After that, the operation is started by switching to the OFF state. The user apparatus is configured to be operated by two or more myoelectric switches, and the operation of the user apparatus is stopped when all the myoelectric switches are turned on.

As a safety technology at the time of start-up, there are cases where the EMG switch is turned on due to the influence of disturbance noise. By using the present invention, the system prevents the system from starting operation when it is not intended due to noise contamination. be able to. Further, involuntary movement can prevent the system from starting operation when it is not intended.
As a safety technique at the time of stoppage, even if noise is mixed and the switch cannot be turned off, the operation is stopped and it is safe. In addition, when an emergency stop is necessary, such as immediately before a collision with a wall or just before falling to a step, the operator may panic and excessively strain muscles. In this case, the myoelectric switch may be turned off. Although difficult, the present invention is safe because it stops the operation.

  Hereinafter, the present invention will be described based on examples. FIG. 1 is a state transition diagram illustrating a safety technique at the time of starting. In FIG. 1, each ellipse indicates each state, and when the condition in parentheses {} beside the arrow is satisfied, a transition is made to the next state according to the arrow. Fig. 1 relates to "safety technology at start-up" when one or more switches are used. The part marked {ON} in the figure indicates that all switches are in the ON state. The switch status other than is displayed as {OFF}. In the following description, the switch represents a myoelectric switch, and is turned on when the myoelectric signal intensity exceeds a threshold value.

First, assume that the state is the “stop, timer reset” state (timer time t = 0). Here, when the switch is turned on, the state transits to the “start standby, timer ON” state.
In the “start standby, timer ON” state (t = t + 1), when the timer time (t) is smaller than the time limit 1 (T1) and the switch is ON, the timer time (t) is the time limit. If the switch is ON in a state where it is 1 (T1) or more and less than the time limit 2 (T2), no transition is made. When the switch is turned off when the time (t) is smaller than the time limit 1 (T1), the state transits to the “stop, timer reset” state. If the switch is turned off when the time (t) is larger than the time limit 1 (T1) and smaller than the time limit 2 (T2), the system is started by changing to the “start” state. When the time (t) becomes equal to or greater than the time limit 2 (T2), the state transits to the “return standby” state.

In “return standby”, the state does not transit to the “stop, timer reset” state until the switch is turned off.
As described above, as a safety technique at the time of starting, in a system operated by one or more myoelectric switches, the operation is started by switching to the OFF state after maintaining the switch ON state for a certain period of time.
Next, safety technology at the time of stopping when two or more switches are used will be described with reference to the state transition diagram shown in FIG. FIG. 2 shows an example of a state transition diagram for determining the operation of the user device (electric wheelchair) operated by two myoelectric switches.

  In FIG. 2, each ellipse indicates each state, and when the condition in parentheses beside the arrow is satisfied, the state transitions to the next state according to the arrow. By turning on both of the two myoelectric switches from each of the forward, left-turning, right-turning, left-hand advance, and right-hand advance states, the operation can be stopped and stopped. As described above, in a system operated with two or more myoelectric switches, the operation is stopped when all the switches are turned on.

(1) Now, assume that the vehicle is in the “stop 1” state shown in FIG.
・ When both switches are turned on, transition to the “Start-up standby” state.
・ If both switches are OFF, the “Stop 1” state is maintained.
・ If one of the switches is turned on, rotate it to the right or left.

(2) It is assumed that the state transits to the “start standby” state.
As in the case described with reference to FIG. 1, both the two switches maintain {ON, ON} for a time limit T1 (for example, 0.5 seconds) or longer and the time limit T2 (for example, 2 seconds). If it becomes {OFF, OFF} within, it will transition to the “forward” state.
-Otherwise, transition to the "Stop 2" state.

(3) It is assumed that the state is changed from the stop 1 state to the “right turn” or “left turn” state.
・ If the same switch state is maintained, “right rotation” and “left rotation” are maintained as they are.
・ Other than that, when the switch changes, that is, not only when both switches are turned off, but also when both switches are turned on, the state transits to the “stop 1” state and stops ( Safety technology).

(4) It is assumed that a transition is made from the start standby state to the “stop 2” state.
・ Transition to the “Stop 1” state only when the switch is set to {OFF, OFF}.
・ Other than that, the “Stop 2” state is maintained.

(5) Assume that the vehicle is in the “forward” state.
・ If the switch is {OFF, OFF}, maintain the “forward” state.
・ When one of the switches is turned on, it changes to “Right forward” or “Left forward”.
・ If the switch is {ON, ON}, transition to “Stop 1” (safety technology at stop).

(6) Assume that the vehicle is in the “right forward” or “left forward” state.
・ If the same switch state is maintained, “right forward” or “left forward” is maintained as it is.
・ If the switch is changed in any other way, transition to “Stop 1” and stop (safety technology at the time of stop).

It is a state transition diagram explaining the safety technique at the time of starting. It is a state transition diagram explaining the safety technique at the time of a stop in the case of using two or more switches.

Claims (2)

In the safety system in the myoelectric interface that detects myoelectricity and operates the user device,
All of the myoelectric switches that are turned on when the myoelectric signal intensity exceeds the threshold are configured to start operation by switching to the OFF state after maintaining the switch ON state for a predetermined time.
Safety system consisting of The safety system according to claim 1, wherein the user device is configured to be operated with two or more myoelectric switches, and the operation of the user device is stopped when all of the myoelectric switches are turned on.

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