Design and Simulation of An Elevator DC Motor Drive with Cascaded Position, Speed and Current Control
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Date
2018-10
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Addis Ababa University
Abstract
An elevator drive control system design is very important in the elevator performance profiles for
the safety and comfort of passengers. These profiles include the slowly accelerating to maximum
recommended speed, smoothly running with specific constant speed, then safely decelerating and
braking to stop when elevator reaches the desired elevator position. The safety and performance of
elevator are highly related to the design and control of its drive system.
The aim of this thesis is to design a cascaded position, speed and current controlled electric elevator
drive system to achieve smoothly operating elevator drive system which increases the accuracy and
precision with which the elevator system responds to position commands.
Before going to the step by step design procedures for creating a cascaded control system the
literature review of theories and backgrounds behind the elevator evolution and drive system, and
also the mathematical modeling of the permanent magnet DC motor parameters and the
regenerative elevator kinematics with load are discussed in detail. Then, design aspects such as
modeling the convertor, tuning parameter of a control system to direct the motor as desired are
carried out. Also analyzing the control performance of the system with and without cascaded
control system through use of computer simulations has been investigated in this thesis work.
Finally, the cascaded position, speed and current controlled elevator DC motor drive has been
modeled in MATLAB Simulink and simulation studies are carried out. The simulation results
demonstrate that the proposed control results in 0% over-shoot for the desired positions of 4m and
40m with corresponding speeds of 0.8 m/s and 2m/s, respectively, during lifting and lowering full
load tests. Zero %-overshoot results also achieved through smooth acceleration and deceleration
with maximum starting and breaking torques of 12NM and 17.5NM for the desired positions of 4m
and 40m respectively. This illustrates that the designed cascaded controller can effectively and
efficiently control the elevator drive operation with passenger comfort in respect of smooth driving
system.
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Keywords
Permanent magnet DC motor, cascaded control system, Position, Speed, Current control