Contactless Picking of Objects Using an Acoustic Gripper

• Main Authors: Marc Röthlisberger, Marcel Schuck, Laurenz Kulmer, Johann W. Kolar
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Actuators
• Subjects: acoustic forces; acoustic levitation; automation; grippers; robotics; ultrasound
• Online Access: https://www.mdpi.com/2076-0825/10/4/70

Acoustic levitation forces can be used to manipulate small objects and liquids without mechanical contact or contamination. This work presents analytical models based on which concepts for the controlled insertion of objects into the acoustic field are developed. This is essential for the use of acoustic levitators as contactless robotic grippers. Three prototypes of such grippers are implemented and used to experimentally verify the lifting of objects into an acoustic pressure field. Lifting of high-density objects (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ρ</mi></semantics></math></inline-formula> > 7 g/cm<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>3</mn></msup></semantics></math></inline-formula>) from acoustically transparent surfaces is demonstrated using a double-sided acoustic gripper that generates standing acoustic waves with dynamically adjustable acoustic power. A combination of multiple acoustic traps is used to lift lower density objects (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ρ</mi><mo>≤</mo><mn>0</mn><mo>.</mo><mn>25</mn><mrow><mi>g</mi><mo>/</mo><mi>c</mi><msup><mi>m</mi><mn>3</mn></msup></mrow></mrow></semantics></math></inline-formula>) from acoustically reflective surfaces using a single-sided arrangement. Furthermore, a method that uses standing acoustic waves and thin reflectors to lift medium-density objects (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ρ</mi><mo>≤</mo><mn>1</mn><mrow><mi>g</mi><mo>/</mo><mi>c</mi><msup><mi>m</mi><mn>3</mn></msup></mrow></mrow></semantics></math></inline-formula>) from acoustically reflective surfaces is presented. The provided results open up new possibilities for using acoustic levitation in robotic grippers, which has the potential to be applied in a variety of industrial use cases.