Latest Papers

ASME Journal of Mechanisms and Robotics

  • Stable Inverse Dynamics for Feedforward Control of Nonminimum-Phase Underactuated Systems
    on January 25, 2023 at 12:00 am

    AbstractAn enhanced inverse dynamics approach is here presented for feedforward control of underactuated multibody systems, such as mechanisms or robots where the number of independent actuators is smaller than the number of degrees of freedom. The method exploits the concept of partitioning the independent coordinates into actuated and unactuated ones (through a QR-decomposition) and of linearly combined output, to obtain the internal dynamics of the nonminimum-phase system and then to stabilize it through proper output redefinition. Then, the exact algebraic model of the actuated sub-system is inverted, leading to the desired control forces with just minor approximations and no need for pre-actuation. The effectiveness of the proposed approach is assessed by three numerical test cases, by comparing it with some meaningful benchmarks taken from the literature. Finally, experimental verification through an underactuated robotic arm with two degrees of freedom is performed.

Development of a Biomimetic Masticating Robot for Food Texture Analysis


Assessing the food texture via mastication is important for advancing knowledge of food properties so as to develop favorable and healthy food products. Oral processing of food by robots can enable an in vitro assessment of food texture by simulating human mastication objectively. In this study, a chewing robot is developed to mimic the rhythmic motion of the molars to enable controllable chewing kinematics and a biomimetic oral environment. The robotic chewing is realized using a 3 degree-of-freedom (DOF) linkage mechanism, which recreates the molar grinding movement based on molar trajectories and chewing cycle durations previously reported in the literature. Moreover, a soft pneumatically actuated cavity is developed to provide a space to contain and reposition the food between occlusions. To regulate the robotic chewing having variable molar trajectories and chewing durations, the mathematical relationship of the linkage’s actuators and molar movements is investigated for the purpose of motion analysis and control. Accordingly, the design of the robot in terms of linkage, oral cavity, and mechatronics system is performed. The built robot is validated by tracing a planned variable molar trajectory while chewing peanuts. The performance of robot chewing is validated by demonstrating the ability of the robot to chew the peanuts similar to that by human through comparison of peanut particle size distributions (PSDs) and particle median size diameters.

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