Robust Control of Robot Manipulator based on QFT and H∞

Robust controllers have been developed by both control techniques QFT and H∞ applied in the waist, shoulder and elbow of a manipulator of 6 degrees of freedom. The design is based on the identification of a linear model of the robot dynamics which represents the non-linearity of the system using parametric uncertainty. QFT control methodology is used to tune the robust PID-controller and pre-filters of the system, and H∞ controllers are obtained by designing the weighting functions and using the MATLAB hinfopt tool. Finally the performance of robust controllers is compared designed based on the calculation and analysis of some behavioral indices.

A DMAIC Framework to Improve Quality and Sustainability in Additive Manufacturing—A Case Study

Additive manufacturing as a key Industry 4.0 technology brings radical changes to how we execute production and services operations. However, this innovative technology has not reached maturity and research and development are still in progress to unleash its full sustainability potential. This paper aims to provide operational guidance to decision makers to jointly improve quality and sustainability performance of additive manufacturing processes. We propose a framework based on the DMAIC (Define/Measure/Analyze/Improve/Control) methodology and comprehensive pool of targeted key performance indicators (KPIs) and illustrate this framework through a single case study. The paper evidences the feasibility of extending DMAIC to the growing additive manufacturing domain to achieve quality and sustainability objectives. The case study uncovered some challenges, e.g., the need for customization to a company/industry context, which must be addressed in order to widely apply the proposed framework successfully.

Clinics in Surgery 1Remedy Publications LLC., | http://clinicsinsurgery.com/ 2021 | Volume 6 | Article 3380 The Effect of Spinal Steroid Injections on COVID-19 Infection and Its Severity

Aim: This paper is to determine the incidence of COVID-19 infection and severe symptoms following spinal steroid injections for pain control. Methodology: This a retrospective observational study based in the department of neurosurgery, Salford Royal Foundation Trust. Study period is from March 23rd, 2020 till December 31st, 2020. 222 patients had these injections during the time period. Data was collected by telephonic interview and online questionnaire. Data was analyzed to find out how many of the people who received steroid injection got COVID infection and how many had severe infection. It was then compared with local infection rates. Results: Out of 222 patients found, 130 patients opted to take part in the survey. Six patients among them had tested positive after the injection and two more patients had symptoms of COVID who have been considered to be positive. Overall, 6.15% of patients who received steroid injections had positive COVID-19 results. 3.85% patients had the infection within 3 months of injection. One patient (0.77%) needed hospital admission due to COVID. The incidence of COVID during this time period in Salford was 6.17% and rate of hospital admission due to COVID was 0.77%. Conclusion: The rate of COVID-19 infection after steroid injection are lower than the local incidence of COVID in Salford during that time period and equivalent to the rate of hospital admission due to COVID. This suggests that a steroid injection in the spine for pain management does not increase the incidence of COVID or cause severe infections.

Design and Analysis of Multi-Device Interleaved Boost Converter Driving an Induction Motor

Electric vehicles are the future of mobility solutions. The electric vehicles are driven by an electric motor with the help of a power electronic interface. The power electronic interface needs to be designed in an efficient way both in mechanical and electrical aspects. This paper proposes the concept of design, simulation and analysis of a 10 kW Multi-Device Interleaved DC-DC Boost Converter (MDIBC) to drive a 4 kW Induction Motor. The motor is driven from the MDIBC through an inverter with SPWM technique. The variation in DC link voltage due to motor is controlled and stabilized to give a constant DC of 400 V. MDIBC consists of semi-controlled switches topology excited by Phase Shifted PWM technique to reduce the ripple current in interleaving inductors. The dual loop control methodology using PI controller is adopted to reduce the ripple in input inductor current and DC link voltage. The open loop simulation and closed loop simulation are done in MATLAB Simulink environment. The simulation results show that the overshoots and steady state error in inductor currents and output voltage are reduced in addition with reduction in current and voltage ripples.

Coordinated Control of Single-Phase End-Users for Phase Load Balancing in Active Electric Distribution Networks

In the paper, a coordinated control methodology of single-phase (1-P) end-users switching operations on the phases of an active electric distribution network (AEDN) has been proposed to obtain a minimum unbalance degree at the coupling common point (CCP) level with the main distribution system. The phase load balancing (PLB) process considers the smart devices that switch the 1-P end-users (consumers and prosumers) from one phase to another to compensate for the phase load unbalance. The proposed methodology has been tested successfully in an AEDN belonging to a Romanian Distribution Network Operator (DNO) containing 114 end-users (104 consumers/10 prosumers) integrated into the Smart Metering System (SMS). The optimal solution leads to a value of the objective function by 1.00, represented by the unbalance factor (UF), which could be identified with the ideal target. A comparative analysis was conducted considering other possible PLB cases (the consumer-level PLB and prosumer-level PLB), obtaining similar values of the UF (1.027 vs. 1.028), slightly higher than in the hybrid-level PLB. Additionally, the significant technical benefits were quantified through an energy-saving of 58.73% and decreasing the phase voltage unbalance rate by 91% compared to the initial case (without PLB). These results emphasized the positive impact of the proposed coordinated control methodology on the PLB process and evidenced its effectiveness and applicability in the AEDNs.