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In this letter, we propose a novel constant-force end-effector (CFEE) to address current limitations in robotic ultrasonography. The CFEE uses a parallel, motor-spring-based solution to precisely generate constant operating forces over a wide range and enable the ultrasound (US) probe to adapt to the abdominal contours autonomously. A displacement measurement unit was developed to realize the acquisition of probe position and precise control of the operating force. Moreover, the operating force can be adjusted online to maintain safety and continuity of operation. Simulations and experiments were carried out to evaluate the performance. Results show that the proposed CFEE can provide constant forces of 4-12 N with displacements of 0-8 mm. The maximum relative error of force generation is 8.28%, and the accuracy and precision for displacement measurement are 0.29 mm and ±0.16 mm, respectively. Various operating forces can be adjusted online during the same operation. Ultrasound images acquired by the proposed CFEE are of equally good quality compared to a manual sonographer scan. The proposed CFEE would have potential further medical applications.

Original languageEnglish
Article number9361110
Pages (from-to)2547 - 2554
Number of pages8
JournalIEEE Robotics and Automation Letters
Issue number2
Early online date25 Feb 2021
Publication statusPublished - Apr 2021


  • Constant force
  • End effectors
  • End-effector
  • Force
  • Force control
  • Online Force Adjustment
  • Probes
  • Robotic Ultrasonography
  • Robots
  • Springs
  • Ultrasonography


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