Autonomous audio heater car: A comprehensive project-based analog design experience

Introduction

Scripted laboratory exercises are often used in the laboratory of engineering and science courses because they make it easy to address specific learning outcomes. However, project- or problem-based learning has become popular because it engages students in an active learning process. It has been shown to be more effective than traditional pedagogy by increasing student interest and higher-level thinking.^1–12 The process of guided discovery can augment that engagement by helping students find and incorporate new information rather than presenting it to them in a traditional teaching approach. ¹³ Team work is often incorporated into the design process because it helps develop communication and collaborative skills and provides a natural environment for peer instruction.^14,15 However, teams can suffer from some students not being prepared to contribute or being unmotivated. ¹⁶ Design competitions motivate students by providing incentives to meet the expectations of other team members and win recognition, higher grades, or other awards.^17–23

The objective of this project was to integrate project-based learning, guided discovery, peer instruction, teaming, and competition with traditional individual pre-lab and lab work to increase engagement, learning, and experience of students in an analog design course, which includes an accompanying theoretical lecture component. The course is part of a comprehensive undergraduate electrical engineering curriculum. It is scheduled in the ninth semester of an 11-semester program. Students taking the course had already taken basic circuit analysis and digital design courses. Many of the students were taking the first course in automatic control in parallel with this course.

The laboratory component had previously used a series of seemingly unrelated and somewhat scripted laboratory exercises. This new approach increased the demonstrated and self-perceived expertise of the students.^24,25 It was intended to provide an engaging and competitive environment in which students would learn a broad range of analog design components individually and incorporate the components into a comprehensive system cooperatively in teams. The individual pre-lab and lab work prepared the students to be effective members of their team, thereby avoiding the frustration of having ill-prepared and disengaged team members. ²⁶

This methodology provided students individual experience working through the full conceive, design, implement, operate (CDIO) process repeatedly on subsystems followed by a single CDIO process working in a team, as shown in Figure 1. Table 1 shows the pedagogical rationale for the methodology of this project. The pre-lab exercises develop the abilities of students to individually conceive of and design analog circuits. The laboratory exercises develop their ability to implement and operate the analog circuits. Providing a system framework and a competition further reinforced their motivation to learn about analog circuits and to be effective in teams. Thus, this approach served to develop the ability of students to work both autonomously and cooperatively, which is essential for surmounting real engineering problems within and outside of academia.

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Figure 1.

Repetition of CDIO process.

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Table 1.

Comprehensive pedagogical rationale.

Character development	Educational objective: Students shall…	Method
		Guided discovery			System framework	Competition (operate)
		Pre-lab exercices (conceive/design)	Lab exercises (implement/operate)	Integration (implement/operate)
Autonomous	Be motivated to learn about analog circuits				X	X
	Have the ability to select components	X
	Have the ability to design circuits	X
	Have the ability to analyze circuits	X
	Have the ability to assemble, test, and debug analog circuits		X
Cooperative	Have the ability to integrate circuits into a system		X	X	X
	Be effective in teams				X	X

This project is similar to other works,^8,27,28–31 except that it includes individual and cooperative team work, an all encompassing conceptual design introduced at the beginning of the course, and a final design competition. Also, the design requirements are different than those of the other works.

Competition framework

Autonomous vehicles appeal to both students and faculty, so one was developed for this project. ²³ Figure 2 depicts the scenario of the competition, which was held in a darkened room to reduce stray light. The following system-level design requirements were introduced during the first laboratory class.

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Figure 2.

Competition concept. The “arena” is a 2 m 2 area demarked with masking tape on the floor. The car begins at the corner diagonally opposite from the beacon with an orientation 90 ° relative to the direct path toward the beacon and with water at 15 ° C . The car finishes within a 25 cm 2 in front of the beacon with water at a temperature indicated by the beacon frequency.

In addition, the following constraints were imposed:

The vehicle shall function autonomously.

The competition judging criteria were as follows:

Proximity of the vehicle to the target.

Satisfying these requirements with standard analog circuits and components was guided by the conceptual design described in the following section.

Conceptual design framework

Often projects are reserved for the end of the semester or multiple and often unrelated projects are introduced throughout the semester.^{3,9,20,21,32–34}

However, in this project, the system conceptual design was introduced in the first laboratory session to establish the framework for all pre-lab and lab activities of the semester.

In this project, the top-level conceptual design, shown in Figure 3, encompasses all of the concepts of the course. It includes three subsystems: motion control, temperature control, and power regulation.

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Figure 3.

Top-level conceptual design, which includes three major subsystems: motion control, temperature control, and power regulation.

Subsystem block diagrams indicated the specific order of the laboratory topics, which is as follows:

Motion control

These topics provided a comprehensive framework for experience with a broad range of analog and mixed signal circuits in a single context.

Analog design laboratory exercises

The laboratory experience included both pre-lab tasks and lab exercises for each of the topics given in the previous section. Pre-lab assignments prepared students for labs by requiring them to perform the following tasks:

Finding data sheets

For guidance, some components were identified in the pre-lab instructions so that students would find appropriate data sheets. The circuit analysis and simulations were guided by the requirements of the subsystems. The following list indicates the pre-lab activities for all of the subsystems.

Motor control

At the beginning of each lab, the professor and students discussed the circuit and component options available to satisfy subsystem requirements. Then, the students could choose to build circuits they had found or those the professor suggested. Each student had to build every circuit individually and demonstrate its performance to the professor. Requiring students to decide which circuits to build individually and those used for the overall project system promoted growth and design thinking. ³⁵

The method of demonstrating the circuit performance was developed by the students and not given by the professor. The professor indicated what had to be proven. Post-lab documentation included a notebook with designs and prototype testing results, including comparisons to pre-lab analyses and simulations.

Student evaluation

The final grade was comprised of pre-lab, laboratory, and project grades with weightings of 20%, 50%, and 30%, respectively. The pre-lab and lab grades were based on individual work, whereas the project grade was based primarily on the competition results and a design report from each team.

In addition to performance on the assignments, a survey was conducted to evaluate the value of the new structure of the laboratory course. The survey included questions in five areas: evaluation of the effectiveness of the pre-labs, labs, and project, evaluation of the time dedicated to each topic, the difficulty of each topic, and level of interest for each topic, an evaluation of the effectiveness of the project team and a peer evaluation. The project team and peer evaluations were based on Oakley et al. ¹⁷

Results

Clearly defined objectives are important, but sometimes absent, from the laboratory course components. ³⁶ In this project, the educational objectives were as follows:

Know the circuits and systems commonly used in analog design.

The project described herein accomplished these objectives. Student performance on the individual pre-lab and laboratory activities demonstrated their knowledge of analog circuits and systems and their ability to analyze them, which comprised the first two objectives. Satisfactory performance on the laboratory exercises using their own procedures and the project demonstrated their ability to design, synthesize, and test analog circuits, thus achieving the third objective. In particular, the students were successful designing, building, testing, and demonstrating the circuits with the expected characteristics.

The class consisted of nine students, who chose their own teams of three students. The results of the first part of the survey, which are shown in Table 2, clearly show that, from the students’ perspective, the laboratory was very helpful to their understanding of the theory and the final project and competition were incentivizing, though less so the competition. No slackers were found in the teams, though the level of commitment of the teams was not uniform across the teams. Not surprisingly, the pre-lab work supported the lab work and the lab work supported the project activities. However, the pre-lab work was not perceived to be as important as the lab work. This was reflected in the student’s reporting a higher tendency to use the circuits presented by the professor, rather than those the students found individually during the pre-lab activities. Generally the students thought the project was impossible for them before the course, whereas after the course, they were much more confident that they could achieve it.

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Table 2.

Results of evaluation of the effectiveness of the pre-labs, labs, and project.

Affirmation	SA	A	I	D	SD
The labs helped understanding of theory	100	–	–	–	–
Labs oriented toward final project were incentivizing	89	11	–	–	–
Labs oriented toward a competition were incentivizing	33	33	22	11	–
The individual labs were useful for completing the project	89	11	–	–	–
Time allocated to the labs was sufficient	11	–	11	56	22
Pre-labs were fundamental for understanding the labs	22	44	22	11	–
The pre-lab circuits were used for the labs	–	33	11	33	22
When the pre-lab circuits were not used, the prelab was still a helpful preparation	33	44	11	11	–
The project was based on the laboratories of one member of the team	–	–	11	33	56
Before this course, I thought the project was impossible	67	22	11	–	–
After the laboratories, I knew how to realize the project	78	11	11	–	–

Note: The numbers represent the percentage of students who responded strongly agree (SA), agree (A), indifferent (I), disagree (D), and strongly disagree (SD).

On average, students reported that the motor laboratory consumed the least amount of time (3.7 hours), whereas the PWM lab took the most time (7.1 hours). The laboratory consisted of two 2-h sessions per week and some lab topics carried over to a second week. However, many lab exercises were completed outside of the designated lab hours. The amount of time spent on the project was strongly correlated with the time spent on labs. However, whereas the lab grades were strongly correlated with the time spent on labs, the project grades were not strongly correlated with the time spent on the project.

The results of the competition widely varied, as shown in Table 3. No team satisfied all of the requirements. However, the degree to which they met the criteria, coupled with the abilities and knowledge demonstrated throughout the laboratory attested to the success of this project.

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Table 3.

Results of the competition relative to the requirements.

Criterion	Team 1	Team 2	Team 3
Travel autonomously to beacon	Yes	Yes	Yes
Stop automatically without impact	No	Yes	No
Set temperature based on tone	No	No	Yes
Generate tone based on temperature	No	No	No
Travel time (s)	8.0	8.0	6.0

The experience could be improved in the following ways:

By providing the mechanical platforms so that less time is spent on tasks not directly relevant to the learning objectives. ³⁷

These enhancements would improve the analog design focus of the project and improve student engagement.

Conclusion

The autonomous audio heater car is a comprehensive project-based analog design experience. It includes signal conversions, signal generation, voltage regulation and protection, mixed signals, sensors, actuators, and control. The individual pre-lab and lab work cross-trained students so that they could be well-prepared and effective members of their teams during the final design and integration processes.

The students participated in the overall design process with guided discovery, rather than pre-contrived lab exercises. Using a conceptual design as the framework for the course from the beginning of the course was motivating for students. It provided the students with an awareness of the interfaces between subsystems and an understanding of how to integrate many distinct circuits.

Although the project was specifically designed for an analog design course, it could serve as a model for other courses in electrical engineering or electronics, including digital design and microcontrollers.