An indirectly controlled high-speed servo valve using piezo actuators
- Authors: Behre, Leander
- Date: 2015
- Subjects: Piezoelectric materials Piezoelectric devices -- Materials , Internal combustion engines Mechatronics Automation
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/50099 , vital:42040
- Description: Since the exhaust emissions legislation for motor vehicles with combustion engines is complicating the manufacturing of environmental yet powerful engines more than ever, automobile manufacturers have approached this challenge by means of downsizing, hybridization of combustion and electric engines and variable valve opening times. In these cases conventional, mechanical valve trains are still used. The subject of this master thesis is the development of a mechatronic control unit as replacement for the camshaft driven valve train of common combustion engines. The system’s aim is a contribution to the progression of the development of modern combustion engines satisfying current demands in terms of economy and efficiency. The developed system is based on the “Full Variable Valve Train” project, founded at the “Institute of Vehicle Construction Wolfsburg” at the “Ostfalia University of Applied Sciences”. An indirectly controlled high speed servo valve that is actuated by a piezoelectric actuator and pressurized hydraulic fluid is being developed. The overall aim is to obtain advantages from a control engineering perspective, being able to reduce the size of the used piezo actuator and hence solve the packaging and regulation issues of the overall system. After manufacturing and improvement activities, a system could be developed that allows a variable control of the engine valve movement. The best results are achieved using a rectangular function for the engine valve actuator. The system allows engine valve operation independent from the crankshaft position and shows the potential to generate higher engine torque and power output while decreasing fuel consumption and emissions at the same time.
- Full Text:
- Date Issued: 2015
- Authors: Behre, Leander
- Date: 2015
- Subjects: Piezoelectric materials Piezoelectric devices -- Materials , Internal combustion engines Mechatronics Automation
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/50099 , vital:42040
- Description: Since the exhaust emissions legislation for motor vehicles with combustion engines is complicating the manufacturing of environmental yet powerful engines more than ever, automobile manufacturers have approached this challenge by means of downsizing, hybridization of combustion and electric engines and variable valve opening times. In these cases conventional, mechanical valve trains are still used. The subject of this master thesis is the development of a mechatronic control unit as replacement for the camshaft driven valve train of common combustion engines. The system’s aim is a contribution to the progression of the development of modern combustion engines satisfying current demands in terms of economy and efficiency. The developed system is based on the “Full Variable Valve Train” project, founded at the “Institute of Vehicle Construction Wolfsburg” at the “Ostfalia University of Applied Sciences”. An indirectly controlled high speed servo valve that is actuated by a piezoelectric actuator and pressurized hydraulic fluid is being developed. The overall aim is to obtain advantages from a control engineering perspective, being able to reduce the size of the used piezo actuator and hence solve the packaging and regulation issues of the overall system. After manufacturing and improvement activities, a system could be developed that allows a variable control of the engine valve movement. The best results are achieved using a rectangular function for the engine valve actuator. The system allows engine valve operation independent from the crankshaft position and shows the potential to generate higher engine torque and power output while decreasing fuel consumption and emissions at the same time.
- Full Text:
- Date Issued: 2015
Student teachers’ perceptions of their school mentors’ interpersonal collegial leadership competencies to develop their work-integrated learning knowledge and skills
- Authors: Mahomed, Carmel Claire
- Date: 2019
- Subjects: Educational leadership , Mentoring in education -- South Africa Student teachers -- South Africa
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: http://hdl.handle.net/10948/42548 , vital:36667
- Description: Mentoring is indispensable for the adjustment of student teachers to the demands of the school work-integrated learning environment. Despite the benefits of mentoring to student teachers, a challenge is the inconsistency of the mentoring programmes within and across schools. An additional challenge is the predominance of bureaucratic models of mentoring, which have the potential of perpetuating a hierarchical approach to mentoring if student teachers use mentor teachers who depend on bureaucratic models of mentoring as role models. Therefore, to ensure that student teachers are exposed to a cross-pollination of expertise from all teachers in the schools, this study proposes a collegial approach to mentoring to determine the impact of the collegial competencies of the mentor teachers on the student teachers’ acquisition of work-integrated learning. A case study in a higher education institution was conducted to obtain data regarding the perceptions of two hundred and forty-one student teachers of their mentor teachers’ interpersonal competencies. The student teachers in this study were all in the final year of their initial teacher education qualification. The respondents comprised student teachers from the Foundation Phase, Intermediate Phase, Further Education and Training and Postgraduate Certificate in Education. Data were gathered using a structured questionnaire. The focus in the questionnaire was on the competencies: interpersonal collegial leadership, communication, empathy, trust, content knowledge and pedagogical content knowledge. The findings revealed that the student teachers’ perceptions of their mentor teachers’ competencies relating to their internal collegial leadership, proficiency in communication, capacity for empathy and ability to establish trust were positive. The mentor teacher competencies of interpersonal collegial leadership, communication, empathy and trust revealed emotional intelligence competencies in their relationships with the student teachers. The findings also revealed that the student teachers' perceptions of their mentor teachers’ competencies relating to content knowledge and pedagogical content knowledge were positive. The mentor teachers’ content knowledge and pedagogical content knowledge revealed their competencies associated with their cognitive skills (IQ) in the school work-integrated environment. The findings also indicated that, in terms of their interpersonal collegial leadership, the mentor teachers were not inclined to harness the expertise of their colleagues to ensure that there was a collegial approach to mentoring among all the teachers in a school. This might be a reason for the inability of some mentor teachers to shift their paradigms from bureaucratic approaches to mentoring to collegial approaches. The adoption of collegial approaches to mentoring with a focus on competencies associated with both EI and IQ has the potential to impact markedly on the enhancement of the professional development of student teachers.
- Full Text:
- Date Issued: 2019
- Authors: Mahomed, Carmel Claire
- Date: 2019
- Subjects: Educational leadership , Mentoring in education -- South Africa Student teachers -- South Africa
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: http://hdl.handle.net/10948/42548 , vital:36667
- Description: Mentoring is indispensable for the adjustment of student teachers to the demands of the school work-integrated learning environment. Despite the benefits of mentoring to student teachers, a challenge is the inconsistency of the mentoring programmes within and across schools. An additional challenge is the predominance of bureaucratic models of mentoring, which have the potential of perpetuating a hierarchical approach to mentoring if student teachers use mentor teachers who depend on bureaucratic models of mentoring as role models. Therefore, to ensure that student teachers are exposed to a cross-pollination of expertise from all teachers in the schools, this study proposes a collegial approach to mentoring to determine the impact of the collegial competencies of the mentor teachers on the student teachers’ acquisition of work-integrated learning. A case study in a higher education institution was conducted to obtain data regarding the perceptions of two hundred and forty-one student teachers of their mentor teachers’ interpersonal competencies. The student teachers in this study were all in the final year of their initial teacher education qualification. The respondents comprised student teachers from the Foundation Phase, Intermediate Phase, Further Education and Training and Postgraduate Certificate in Education. Data were gathered using a structured questionnaire. The focus in the questionnaire was on the competencies: interpersonal collegial leadership, communication, empathy, trust, content knowledge and pedagogical content knowledge. The findings revealed that the student teachers’ perceptions of their mentor teachers’ competencies relating to their internal collegial leadership, proficiency in communication, capacity for empathy and ability to establish trust were positive. The mentor teacher competencies of interpersonal collegial leadership, communication, empathy and trust revealed emotional intelligence competencies in their relationships with the student teachers. The findings also revealed that the student teachers' perceptions of their mentor teachers’ competencies relating to content knowledge and pedagogical content knowledge were positive. The mentor teachers’ content knowledge and pedagogical content knowledge revealed their competencies associated with their cognitive skills (IQ) in the school work-integrated environment. The findings also indicated that, in terms of their interpersonal collegial leadership, the mentor teachers were not inclined to harness the expertise of their colleagues to ensure that there was a collegial approach to mentoring among all the teachers in a school. This might be a reason for the inability of some mentor teachers to shift their paradigms from bureaucratic approaches to mentoring to collegial approaches. The adoption of collegial approaches to mentoring with a focus on competencies associated with both EI and IQ has the potential to impact markedly on the enhancement of the professional development of student teachers.
- Full Text:
- Date Issued: 2019
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