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Browsing by Subject "Motor Control"

Now showing 1 - 2 of 2
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    Non-Linear Characterization and Control of Interior Permanent Magnet Synchronous Machines
    (2022-06) Chandrasekaran, Visweshwar
    The dissertation will present a systematic process for advanced characterization and control of a popular class of synchronous machines called Interior Permanent Magnet Synchronous Machines (IPMSM). The IPMSM machine exhibits several non-linear properties such as flux saturation and cross-coupling to name a few. Knowledge of the non-linear properties of the machine requires access to advanced design tools such as Finite Element Analysis (FEA) which may not be easily accessible within industries that do not design or manufacture these motors. The performance and efficiency of these motors are reliant on precise knowledge of advanced parameters. This body of work develops into two focus areas - experimental characterization of the IPM machine and Maximum Torque Per Amp (MTPA) based control of the machine using the experimental data. Firstly, the dissertation proposes an experimental method for extraction of Direct (D) and Quadrature (Q) axis flux linkages of the IPMSM considering both saturation and cross-magnetization effects over the entire range of the machine’s rated current. A key constraint placed is a standstill estimation of the machine in its targeted application. A novel method for generating the current pulse pattern is proposed which enables the automatic creation of 2D Flux Linkage maps of the motor using any standard controller. Analytical expressions are developed to determine the constraints for pulse pattern considering the power converter-based current control and minimizing rotor movement during the test. The flux maps obtained experimentally are seen to match the FEA-generated equivalent within an acceptable tolerance of error. The second focus area consists of developing MTPA control schemes that address practical issues such as complex offline/online calculations/excitation methods seen in classic literature. Initial research focused on developing an offline numerically efficient MTPA trajectory generation that uses FEA data to create a torque profile related to the optimal solution of net space vector current and corresponding current angle. Further research removed the dependency of the offline MTPA trajectory generation scheme on the FEA dataset by developing a method that utilizes simple motor datasheet parameters to get an initial non-efficient trajectory. This trajectory is fine-tuned during motor operation (online) via a novel discrete extremum-seeking state controller. While the offline method is shown to execute with minimal computational demand in a 32-bit MCU controller, the online method is shown to have comparable real-time performance while achieving equivalent MTPA tracking accuracy without introducing electrical or mechanical instability. Both methods have been implemented in a classic Field Oriented Control (FOC) scheme for the IPM motor using a standard 2-level Voltage Source Inverter (2L-VSI) prototype supplied from a 650V DC power supply. The methods have been experimentally verified on a 3 HP dynamometer with custom-built data acquisition instrumentation as well as software. Experimental results show good correspondence to simulations thus proving the effectiveness of the proposed methods.
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    Study of scapular muscle latency, shoulder kinematics and muscle activity in people with and without shoulder impingement.
    (2009-08) Phadke, Vandana
    Background and significance: Shoulder impingement is a common shoulder pathology which is associated with changes in kinematics and muscle activity around the shoulder joint. The changes in muscle activity are theorized to be caused by changes in motor program strategies controlling the smooth and coordinated movements at the joints. Changes in muscle latencies, especially feed forward contractions, indicate alterations in these motor control programs. The purpose of the study was to assess for differences in the latencies and deactivation times of scapular muscles between subjects with and without shoulder impingement. Research Methods: Twenty five healthy subjects and 24 subjects with impingement were recruited. Scapulothoracic and glenohumeral kinematic data were collected using an electromagnetic system. Simultaneously myoelectric activities using surface electrodes from upper trapezius, lower trapezius, serratus anterior and anterior fibers of deltoid were collected as subjects raised and lowered their arm in response to a light cue. Data was collected during unloaded, loaded and after performing repetitive arm raising motion conditions. Analysis: The ratios of the number of feedforward contractions during trials were compared by chi square analysis across groups and conditions. The other variables were analyzed using 2 or 3 way mixed model ANOVAs. Results: The percentage of trials showing feed forward contractions was higher for upper trapezius and lower trapezius in the unloaded condition and lower for serratus anterior in the condition after repetitive motion for the subjects with impingement as compared to healthy subjects. Subjects with impingement also demonstrated significantly earlier contraction of upper trapezius and an earlier deactivation of serratus anterior during lowering of the arm as compared to the healthy subjects. All subjects exhibited an earlier activation and delayed deactivation of lower trapezius and serratus anterior in conditions with a weight held in hand. The study found decreased scapular upward rotation, decreased posterior tilt and a less anterior plane of elevation in combination in subjects with impingement using logistic regression analysis. No significant group differences were found for muscle activity as a percentage of the reference contraction. Discussion and conclusions: The subjects with impingement showed some significant differences for muscle activation and deactivation times to indicate differences in motor control strategies. Rehabilitation measures should incorporate appropriate training measures in tandem with strengthening and stretching exercises to focus on improving movement patterns and muscle control.