SuperFlow AutoDyn, Руководство оператора

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Control Modes
11-4 AutoDyn Chassis Dynamometer Operator Manual
11.2.1 Manual (Position) Control Mode
Also called “open loop” control mode, this mode only sends a position signal to the corresponding
actuator (the load controller or the throttle controller). It does not take the feedback signal into
consideration and thus has no self-correcting effect. The manual (position) control mode is used
whenever the control signal is only determined as a “% of full range” of the controller actuator.
With the dynamometer load controller in the manual control mode, the load on the dynamometer
is determined by the position of the load control valve (or the electric current in the dynamometer
eddy current coils). The operator determines a “% of load” value which sets the valve (or current)
to a particular percentage of its full operating range. The resulting load on the dynamometer is
purely a function of water flow through the valve (or current through the coils) at that position,
which combines with the rotational speed of the absorber to create a resisting torque. The valve
position (or electric current) is not affected by any feedback signals.
The % of load setting does not correspond to any specific torque value but rather to a torque curve
as a function of speed. In this mode the operator can easily stall the engine by applying excessive
load.
The manual mode is typically used for diagnostic purposes or to warm up the engine (this is only
practical if the appropriate position is approximately known by experience).
If a throttle control option is installed, when it is in the manual control mode, the system will
control the engine throttle to a given percentage (%) of full travel. No actual throttle position
feedback is provided; the percentage of full travel indicated by the control system corresponds to
the value at the throttle actuator, not the actual throttle position of the engine. If the linkage
between the throttle actuator and the throttle valve is not adjusted properly for end stops and
travel (or if it is nonlinear), it causes a difference between actuator position and actual throttle
position.
11.2.2 Servo Control Mode
Also called “closed loop” control mode, this mode sends a position signal to the corresponding
actuator (the load controller or the throttle controller), measures the resulting change in the
controlled variable, calculates the error, and refines the position signal until the desired set point
is reached and maintained. The servo control mode is used whenever the control signal is tied to a
measured variable.
Speed Control Mode
This is the most common dynamometer control mode used during automated tests. Speed control
mode is an excellent example of a closed-loop control system because the feedback signal and the
error signal influence the control output. The load control valve or eddy current is controlled by
the system to maintain a desired dynamometer speed (the set point). The load position will be
modulated so the load applied by the absorber matches the speed output of the dynamometer to
the desired operating point.
Speed control is used in all automated tests that step through the engine rpm band while
recording data. Speed control can also be used to maintain the vehicle at a constant speed while
the throttle is varied. However, if the throttle is not opened sufficiently for the vehicle to reach the
desired set point, load control will never activate. Only when the vehicle speed is at or above the
set point will the load controller start to vary the load on the dynamometer to bring the feedback
signal to the set point. This means a transition phase usually occurs where the set point is
exceeded before the feedback signal settles to the desired value. This is called “overshoot” and is a