Project

# Title Team Members TA Documents Sponsor
39 A Morphable Bionic Robotic Fish with Dual-Mode Propulsion Enabled by a Transformable Caudal Mechanism
 Bowen Zhang
Kaijun Zheng
Libin Wang
Xuanyu Ke
 design_document1.pdf
final_paper1.pdf
final_paper2.docx
video1.mp4
 Hua Chen
# Problem
Most existing underwater robotic fish rely on only one propulsion method, which limits their adaptability across different tasks and environments. Bioinspired tail propulsion is typically smooth, quiet, and energy-efficient, making it well suited for steady swimming and maneuvering. In contrast, propeller-based propulsion can provide higher speed, faster acceleration, and stronger turning capability. However, integrating both propulsion methods into a compact robotic fish remains technically challenging, since the tail structure, actuation mechanisms, and control strategies often impose conflicting design requirements. Therefore, there is a need for a transformable underwater robotic platform that can switch between different propulsion modes and better adapt to diverse operational scenarios.
# Solution Overview
Our project aims to develop a transformable underwater robotic fish capable of multi-mode propulsion. The system integrates a waterproof electronic enclosure, a bioinspired tail-swing actuation mechanism, and a caudal-fin-to-propeller morphing structure within a compact robotic body. In one mode, a servo-driven tail produces periodic left-right oscillations to achieve fish-like swimming behavior with smooth and efficient motion. In the other mode, the rear-end transformation mechanism re-configures the caudal fin into a propeller structure driven by a brushless motor to generate higher thrust for rapid movement. A manual control system is used to command both locomotion and propulsion mode switching. Through this design, the robotic fish provides a promising platform for studying adaptive underwater locomotion in different environments.
# Solution Components
## Waterproof Electronic Enclosure Subsystem
- A waterproof shell used to protect internal components from water ingress during underwater operation.
- An embedded control PCB used to coordinate sensing, actuation, and system-level control.
- A battery module used to provide onboard power for the robotic fish.
- An IMU used to measure motion state and orientation during swimming.
- Electrical and communication interfaces used for subsystem integration and testing.
## Bioinspired Robotic Fish Tail-Swing Actuation Subsystem
- A set of 3D-printed mechanical structural components designed to support the tail-swing motion.
- Servos used to drive the oscillatory motion of the robotic tail for bionic propulsion.
## Caudal Fin-to-Propeller Morphing Subsystem
3D-printed fin-like components designed to support both fin and propeller configurations.
- A morphing mechanism used to transform the caudal fin into a propeller-based propulsion structure.
- A brushless motor used to drive rotational thrust in propeller mode.
## Manual Control System
- A controller used to manually command the robotic fish’s movement and switch between propulsion modes.

# Criteria of Success
The project will be considered successful based on the following criteria.
## Stable Underwater Locomotion
The robotic fish must be able to perform basic underwater locomotion, including stable forward swimming and directional steering in a water environment.
## Reliable Mode Transformation
The tail transformation mechanism must successfully switch between the bionic flapping mode and the propeller propulsion mode while submerged, and the structure must remain stable and mechanically reliable throughout the transition. Also, both propulsion modes can operate normally.
## Data Acquisition and Evaluation
The system must be capable of collecting key operational data so that the performance of the two propulsion modes can be evaluated and compared.
# Members and Work Distribution
- Zhang, Bowen (ME): Mechanical design and assembly
- Ke, Xuanyu (ME): Mechanical design and assembly
- Zheng, Kaijun (EE): Electronic system design and testing
- Wang, Libin (ECE): Control algorithm development and system programming

A Micro-Tribotester to Characterize the Wear Phenomenon

Shuren Li, Boyang Shen, Sirui Wang, Ze Wang

A Micro-Tribotester to Characterize the Wear Phenomenon

Featured Project

**Problem**

Many research efforts have been made to understand the complex wear mechanisms used to reduce wear in sliding systems and thus reduce industrial losses. To characterize the wear process, coefficient of friction needs to be measured “not only after completion of the wear test but also during the wear test to understand the transitional wear behavior that led to the final state”.(Penkov) In order to improve the effectiveness and efficiency of these research methods, it is necessary to improve the instrument used to characterize the wear phenomenon to better measure the friction coefficient of the material. Although the instrument can be applied on all solid samples, we will use silicon wafer coated with SiO2 as our specimen targeted object.

**Solution Overview**

The objective of the experiment is to evaluate the wear phenomenon of the sample during the sliding test so as to obtain the wear information of the material. We will design planar positioning and force sensing system to get the move and force information of our objects. To collect the data of vertical load and horizontal friction, 2 force sensors are mounted on linear rails to minimize the radial force and ensure that only the axial forces are collected. Then, the coefficient of friction can be calculated by equation:

![](https://courses.grainger.illinois.edu/ece445zjui/pace/getfile/18615)

And to determine the relationship between the coefficient of friction and the state of wear, we use a microscope to monitor the state of wear at a given location in the wear track and evaluate the wear process during each sliding cycle. In this way, we can investigate the wear transition processes with respect to the sliding distance then transport our data to a computer. Finally, we will design our data processing method in the computer to successfully obtain an acceptable result in the margin error.

**Solution Components**

1. Motion Platform: This subsystem includes a linear actuator that moves the sample in reciprocating motion along X-axis, a stationary counter surface that applies constant vertical load onto the sample, and another actuator that compresses the spring and provides a vertical load to the counter sample.

2. Specimen and Counter surface: We will test the wear and friction between the specimen and the counter surface during the sliding test. A 10 × 10 mm^2 silicon (Si) wafer coated with 50 nm thick SiO2 will be used as the specimen and a stainless-steel ball with a diameter of 1 mm was used as the counter surface.

3. Sensors: This subsystem includes two force sensors that measure the vertical load and horizontal friction. The Load Sensor should assemble along with the Z-axis actuator. To measure the friction without the effect of load, we assemble the Load Sensor and Friction Sensor sensor on the Linear Rails, as the photo attached shows. Since the sensors are strain gauges and only outputs, small changes in resistance, amplifiers, and ADC are needed to collect the signal and send converted data to the computer.

4. Data Processing: This subsystem includes acquiring raw data of load and friction on the computer, applying necessary filters to reduce noise and improve accuracy, and plotting the result that reflects the relationship between the sliding cycles and coefficient of friction for our sample.

![](https://courses.grainger.illinois.edu/ece445zjui/pace/getfile/18611)

**Criterion for Success**

1. Motion platform can perform precise reciprocation. The control system can effectively control the number and speed of reciprocating motion.

2. The acquisition unit can collect data effectively and can transfer the data that can be processed to the computer.

3. On a computer, the raw data can be processed into a readable graph based on algorithms set up. By analyzing the graph, the relationship between the data and the expected results can be correctly obtained.

**References**

Penkov OV, Khadem M, Nieto A, Kim T-H, Kim D-E. Design and Construction of a Micro-Tribotester for Precise In-Situ Wear Measurements. Micromachines. 2017; 8(4):103. https://doi.org/10.3390/mi8040103