Advancing Miniature Quadrupedal Piezoelectric Robots
In a paper recently published in the journal Biomimetics, researchers from China designed and manufactured a miniature quadrupedal piezoelectric robot called small modular robot-o (SMR-O) capable of achieving rapid and agile locomotion. The robot employs a novel spatial parallel mechanism for its transmission system and utilizes an innovative manufacturing method for piezoelectric actuators to enhance their output performance.
Background
Miniature robots, defined as robots with a size less than 10 cm, have attracted considerable attention in various fields including search and rescue, medical diagnostics, exploration, and fault detection in narrow environments. Piezoelectric elements have emerged as popular actuators for these robots due to their rapid response, high power density, and immunity to electromagnetic interference. However, the motion performance of miniature robots can be affected by factors such as actuator design, transmission mechanism, exoskeleton structure, and control methods.
About the Research
In this study, the authors introduced the SMR-O miniature quadrupedal piezoelectric robot, consisting of powertrains, exoskeletons, eight piezoelectric actuators, and four legs. The robot incorporates a spatial parallel mechanism known as a parallel kinematic mechanism (PKM), featuring five degrees of freedom and three limbs. This configuration facilitates two degrees of freedom of motion, encompassing three rotations and two translations.
Drawing inspiration from the motion joints of insects, the PKM enables the robot to swing and lift effectively. Its gait replicates the familiar trot gait observed in insects, achieved by manipulating the phase of the drive signals to the eight actuators. This phase control enables the robot to move forward and execute turns by adjusting the phase inputs appropriately.
Furthermore, the researchers developed a novel manufacturing method for piezoelectric actuators, utilizing discrete patterned lead zirconate titanate (PZT) pieces during material stack to eliminate the need for cutting PZT with a high-power laser. The actuator’s base is alumina, with the PZT alumina interface reinforced by carbon fiber. This approach resulted in a 32% increase in the actuator’s output force compared to those using flame retardant 4 (FR-4) as the base and attachment material. FR-4 is a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame-resistant (self-extinguishing).
The transmission system of the robot was modeled and analyzed, with its parameters optimally designed. Leveraging the powertrain model, the link lengths of the transmission mechanism and the robot’s leg lengths were optimized to maximize the leg output force. Each leg can achieve a maximum output force of 26 mN, surpassing the force required for successful trot gait locomotion by 138%. Additionally, the authors conducted measurements on the actuators’ output capability and the legs, as well as the frequency response of the powertrain and the robot’s locomotion performance.
Research Findings
The outcomes showed that the presented quadrupedal piezoelectric robot achieves a peak speed of 48.66 cm/s and can carry a payload of 5.5 g when its powertrain reaches a resonant state. This represents a significant improvement in locomotion performance compared to a speed of 5.32 cm/s and a payload capacity of 2.5 g at a frequency of 10 Hz. The robot demonstrated the ability to swing and lift effectively, facilitated by its innovative spatial parallel mechanism-based transmission.
The miniature quadrupedal piezoelectric robot holds promise for diverse applications across various fields.
- Search and rescue: Capable of navigating through complex terrains and confined spaces, the robot can be equipped with sensors or cameras to locate survivors or identify hazards.
- Exploration: With its agility and adaptability, the robot can explore remote or inaccessible environments such as caves, volcanoes, or planets, facilitating data collection or sample retrieval.
- Medical diagnostics: Leveraging its compact size and maneuverability, the robot can be deployed for tasks within the human body or blood vessels, including drug delivery, tissue biopsy, or surgical procedures.
- Fault detection: Equipped with sensors and advanced mobility capabilities, the robot can inspect pipelines, wires, or structures to identify faults such as cracks, leaks, or corrosion, aiding in maintenance and repair efforts.
Conclusion
In summary, the SMR-O demonstrated remarkable effectiveness in achieving rapid and agile locomotion. Its parallel transmission mechanism and innovative manufacturing approach notably enhanced its output force and reliability.
Despite its mass of 1.8 g and compact body length of 4.6 cm, the robot exhibited impressive capabilities, reaching speeds of up to 48.66 cm/s and boasting a payload capacity of 5.5 g. The authors successfully showcased the feasibility and efficacy of the robot’s design and fabrication, offering a compelling solution for the advancement of miniature robots.
Moving forward, the researchers acknowledged several limitations and challenges and suggested directions for future work. They recommended improving the control method of the robot, such as using feedback control or adaptive control, to achieve more stable and robust locomotion.
Additionally, they proposed developing more advanced sensors and power sources for the robot, such as wireless communication, vision, or energy harvesting, to enhance the autonomy and functionality of the robot. Furthermore, they emphasized exploring more complex gaits and motions for the robot, such as jumping, climbing, or swimming, to expand the scope of application of the robot.
Journal Reference
Wu, G.; Wang, Z.; Wu, Y.; Zhao, J.; Cui, F.; Zhang, Y.; Chen, W. Development and Improvement of a Piezoelectrically Driven Miniature Robot. Biomimetics 2024, 9, 226. https://doi.org/10.3390/biomimetics9040226, https://www.mdpi.com/2313-7673/9/4/226.
