What is Force Feedback?
Force Feedback as it applies to manipulator arms is not a " Jedi " power, but rather a
method of control which allows the operator to feel what the remote manipulator arm is
Small electric actuators on the joints of the operator's hand controller attempt to move the
controller in response to forces sensed at the manipulator. Because the operator is
holding the controller while operating the manipulator, he or she feels these forces as the
controller tries to move. This force information is of great value when operating a
manipulator arm from a remote location. In a situation where you can normally only see
what's going on, the ability to also "feel" what's going on, dramatically improves the
operator's level of awareness.
Many of our competitors claim to have this capability when in reality few have little more
than a research project, and certainly not a commercially viable product. By comparison,
90% of the manipulator systems Kraft delivers are force feedback systems which are used
everyday in the most demanding applications.
Force feedback is not a luxury, but rather an element of control that is fundamental to
improving operator performance. Force feedback is something that must be experienced
first hand, and for those who have had the opportunity, the value of this technology is
In order for you to draw your own conclusions, we invite you to visit our facility for hands
on operation of a manipulator arm with and without force feedback.
Force Feedback: The Myths The Facts
Force feedback manipulators are delicate devices that provide the operator with a sense of touch and feel.
A 7-function hydraulic force feedback manipulator arm, and a standard 7-function
position controlled hydraulic arm are very much alike. Both types are typically very
rugged and powerful, while providing long reach and a heavy lift capability. The primary
difference between a standard position controlled arm, and a force feedback manipulator
arm, is the way in which the arm is being controlled.
A standard position controlled manipulator responds directly to the operators commands
as he or she moves the controller. Moving the controller at one end makes the
manipulator arm move at the other end. When the controller is not being moved, the
manipulator arm remains rigidly in place awaiting the next command. Pushing or pulling
on the manipulator itself will not make anything happen. The manipulator arm will only
respond to movement of the controller. This is called unilateral control.
A force feedback manipulator system works very much the same way, but in both
directions. If you move the controller the manipulator arm will move, however, if you push
or pull on the manipulator arm itself, the controller will move, and the two will move
together. This is called bilateral control.
Bilateral control is accomplished by placing electric actuators on the individual joints of
the operator's controller. These actuators respond to forces acting upon the manipulator
to provide movement of the controller, and in the process convey force feedback to the
Force feedback manipulator systems are not needed.
At one time, people also said the electric light was not needed.
The fact is, force feedback dramatically improves operator awareness, and allows the
manipulator operator to control the amount of force the manipulator arm can exert at the
work site. Unlike conventional hydraulic manipulator arms which must rigidly withstand all
the forces acting upon them, force feedback manipulator arms with bilateral control have
the ability to move in compliance to these forces. The ability of the operator to control
the amount force exerted by the manipulator, and the ability of the manipulator arm itself
to respond to force, as opposed to resisting it, dramatically reduces the risk of damage
to the manipulator arm and the work site. All joints in the manipulator arm are compliant
(can move) to keep the arm from breaking.
Force Feedback manipulator arms are more fatiguing to operate.
It's true that force feedback makes the manipulator operator perform a small
percentage of the work, this is in fact the essence of force feedback, however, the
intuitive nature of a good force feedback control system greatly reduces the mental
fatigue associated with long periods of manipulator operation. Reducing mental fatigue
is most important, as the amount of force feedback (physical fatigue) the operator
experiences is variable and can be adjusted or turned off altogether to satisfy his or her needs.
Force feedback manipulator systems are more complicated and therefore unreliable.
No one buys a black & white TV because they believe a color TV would be
unreliable. Color TV sets are more complicated, but very reliable.
The fact is, that for over 20 years Kraft force feedback manipulator systems have
demonstrated exceptional performance, and reliability while being used in military, nuclear,
aerospace, electric utility, and offshore oil and gas applications world wide. Force
feedback technology does not reduce the overall reliability of a manipulator system. In
fact, the benefit of having force feedback to the operator significantly reduces the risk of
damage to the manipulator arm when operating from a mobile platform, and in other
Force feedback manipulator systems are not field serviceable.
In reality, Kraft force feedback manipulator systems, in terms of hardware, are not
significantly more complex than standard position controlled manipulator systems. All
Kraft manipulator systems are well documented and completely field serviceable. Modular
electronics and comprehensive self diagnostic routines, allow the manipulator operator
to quickly diagnose a problem and bring the manipulator back on line.
Force feedback manipulator systems are too expensive.
Kraft Force feedback manipulator systems are competitively priced to compete with
conventional non force feedback systems, and often the benefit of having a force
feedback system does not cost any more.