30 | Ottobock
8E38=9, 8E39=9, 8E41=9
9.4 Control mode 4:
VarioDual
Control with 2 electrodes
With this control mode, the opening speed is determined by the strength and speed of the muscle
contraction. The closing speed depends on the speed of the muscle relaxation. The following or
simultaneous electrode signal to the second electrode determines the grip force. Another, stronger
electrode signal to the second electrode increases the grip force.
Electrode 1:
Opening:
Proportional. The opening speed is determined by the speed of the muscle contrac-
tion.
Closing:
Proportional. The closing speed is determined by the speed of the muscle relaxation.
Stopping:
By very slow muscle relaxation to the electrode; the MyoHand VariPlus Speed stops
in an opened position.
Electrode 2:
Grasping:
The level of the electrode signal to the second electrode determines the build-up of
the grip force. The maximal grip force is approx. 100 N.
Example 1: After opening, the amputee relaxes the muscle at any speed. The MyoHand VariPlus
Speed closes proportionally to the speed of the muscle relaxation. The object is
grasped with minimal force.
Example 2: After grasping as described in example 1, the MyoHand VariPlus Speed is to grasp
the object with a higher grip force. For this purpose, the amputee must create an
electrode signal to the second electrode. Proportionally, a grip force of up to approx.
100 N can be built up.
Control
mode 4
OPEN
CLOSE
Indication
VarioDual Increasing electrode
signal through mus-
cle contraction to
the first electrode
Declining electrode signal through muscle re-
laxation to the first electrode
or:
Sustained electrode signal to the second
electrode
For am-
putees
with two
strong
electrode
signals
Speed and strength
of muscle contrac-
tion to the electrode
Grip force:
Proportional to the signal strength to the sec-
ond electrode. If only the first electrode is
used, the MyoHand VariPlus Speed closes
up to the minimal grip force.
Grip force increase:
By another, stronger electrode signal to the
second electrode. After gripping once with
maximum force, the EMG signal required to
OPEN the Hand will be set to a higher value.
Opening the MyoHand VariPlus Speed with
unwanted electrode signals is prevented.
Speed:
Proportional to the
increase of the elec-
trode signal
Adjustment regula-
tor A
Speed:
Proportional to the decline of the electrode
signal to the first electrode / proportional to
the signal strength to the second electrode
Adjustment regulator A
