06-10-2012, 04:01 PM
Sensor Free Power Assisting Control Based on Velocity Control and Disturbance Observer
8_Sensor Free Power Assisting Control Based on.pdf (Size: 1.07 MB / Downloads: 29)
INTRODUCTION
Recently welfare systems including power assisting
system are emerging as new application of the control
theory. In the industrial application of control, precise
position, velocity, force tracking and strict disturbance
rejections became the main object of control. But in
the case of welfare application, other factors such as
smooth control are more important than precise tracking
or strict disturbance rejections. And those applications are
located so near human that control design should be more
considerate. The plant is likely to endanger the operator
when the controller fails to assist properly. This point
makes control design for power assisting control difficult.
Application to a Wheelchair
There are many kinds of power assisted wheelchairs,
but most of all have some force sensors to measure human
force to assist. These sensors which are installed in rims
or handles only measure forces that work on limited parts
of wheelchair. If sensor is installed in rim, a helper does
not benefit from the assisting control, and if sensor is in
handle for a helper, a rider will not benefit. Moreover
those force sensors are expensive and are one reason that
makes the power assisted wheelchairs cost that much.
The proposed controller can work as a power assisting
controller that does not need force sensing. Here, the
assistance characteristic of the control design is experimented
using a wheelchair.
NUMERICAL CONSIDERATION OF CONTROL PARAMETERS
A novel control design method has been proposed
in section II-C, but the parameters left unexplained. In
this section, relationship between the parameters and
control performance is clarified. To this end, the following
discussion is restricted to the application to the powerassisted
wheelchairs, and time responses with step torque
input to the wheelchair will be checked.
CONCLUSION
In this paper, we have suggested that motor systems
should be sensitive to disturbance when a person works
as disturbance, and propose a control design that will
sensitize the plant to the disturbance. It is true that the
proposed controller only works well where there is no
other disturbance than human force. We may need other
disturbance classification method to cope with this case.
But as we said in the introduction, the proposed controller
is necessary as a basic control unit. Experiments done in
this paper tells that the proposed controller’s ability as
this basic control unit.