Flexible virtual fixtures for human-excavator cooperative system

The coordination of human operation and automation of robotic excavators is a key problem in human-excavator interaction. To integrate the active decision of the operator and the accurate control of the machine system, flexible virtual fixtures are proposed to control trajectory of the robotic excavator. The flexible virtual fixtures rely on the current position at the bucket tip. The input signal of the restricted motion direction is weakened by introducing the flexibility coefficient kτ, and choosing kτ low imposes the additional constraint that the robotic excavator is stiffer in the restricted motion direction. In this way, a human-excavator cooperative system is built. Then, different tasks were designed to validate the performances of the proposed flexible virtual fixtures, and different operation ways were compared in terms of tracking accuracy, safety and operating time. The results have demonstrated that the flexible virtual fixtures in the trajectory tracking process not only guarantee the tracking precision, but also ensure a good obstacle avoidance ability. Also, the tele-operators can save a lot of time during the tele-operation process. In the future work, we will introduce the environmental identification results to assist the operator to choose a more reasonable kτ value. •A human-excavator cooperative system is built.•The active decision of the operator and the accurate control of the machine system are integrated.•A flexibility coefficient kτ is introduced to impose the additional constraint in the restricted motion direction.•Effectiveness of the proposed flexible virtual fixtures is validated by experiments.•A truly remote-controlled robotic excavator is built for the tele-operation process.