An official website of the United States government
The robotic spine has a lot of potential for snake-like, quadruped, and humanoid robots, as it can improve their mobility, flexibility, and overall function. A common approach to developing an articulated spine uses geared motors to imitate vertebrae. Instead of using geared motors that rotate 360 degree, a bioinspired gearless electromechanical actuator was proposed and developed as an alternative, specifically for humanoid spine applications. The actuator trades off angular flexibility for torque, while the geared motor trades off speed for torque. This article compares the proposed actuator and conventional geared motors regarding torque, acceleration, and copper loss for a vertebra's angular flexibility. When its angular flexibility is lower than 14∘, the proposed actuator achieves higher torque capability without gears than with conventional motors. Lower angular flexibility, which means smaller airgaps, allows the proposed actuator to produce a much stronger torque for the same input power. The actuator's nonlinear electrical and mechanical dynamics models are developed and used for position control of a six-module distributed spine. In addition, two different position-control architectures are developed: an outer loop proportional-integral (PI) position controller with an inner loop PI current controller and an outer loop PI position controller with an inner loop PI torque controller.
more »
« less
Neuromuscular embodiment of feedback control elements in Drosophila flight
While insects such asDrosophilaare flying, aerodynamic instabilities require that they make millisecond time scale adjustments to their wing motion to stay aloft and on course. These stabilization reflexes can be modeled as a proportional-integral (PI) controller; however, it is unclear how such control might be instantiated in insects at the level of muscles and neurons. Here, we show that the b1 and b2 motor units—prominent components of the fly’s steering muscle system—modulate specific elements of the PI controller: the angular displacement (integral) and angular velocity (proportional), respectively. Moreover, these effects are observed only during the stabilization of pitch. Our results provide evidence for an organizational principle in which each muscle contributes to a specific functional role in flight control, a finding that highlights the power of using top-down behavioral modeling to guide bottom-up cellular manipulation studies.
more »
« less
- Award ID(s):
- 1845673
- PAR ID:
- 10501174
- Publisher / Repository:
- American Association for the Advancement of Science
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 8
- Issue:
- 50
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
This paper reports on a study whose goal is to control the tissue temperature at a specific spot during laser surgery, for the purpose of, e.g., inducing coagulation or sealing blood vessels. We propose a solution that relies on the automatic adjustment of the laser focus (and thus how concentrated the laser beam is), combined with the use of an infrared thermal camera for non-contact temperature monitoring. One of the main challenges in the control of thermal laser-tissue interactions is that these interactions can be hard to predict due to the inherent variability in the molecular composition of biological tissue. To tackle this challenge, we explore two different control approaches: (1) a model-less controller using a Proportional- Integral (PI) formulation, whose gains are set via a tuning procedure performed on laboratory-made tissue phantoms; and (2) a model-based controller using an adaptive formulation that makes it robust to tissue variability. We report on experiments, performed on four types of tissue specimens, showing that both controllers can consistently achieve temperature tracking with a Root-Mean-Square Error (RMSE) ≈ 1 ◦C.more » « less
-
Zonta, Daniele; Su, Zhongqing; Glisic, Branko (Ed.)Civil infrastructures are susceptible to damage due to external forces such as winds and earthquakes. These external forces cause damage to buildings and different civil structures. To prevent this, active control systems are executed. These systems use sensors to measure the displacement of the infrastructure, then actuators are utilized to provide a force that counteracts that displacement. In this study, a Proportional Integral Derivative (PID) controller was used to minimize the impact of an earthquake disturbance on multi-story structures. The proportional, integral, and derivative gains of the controller were obtained using Particle Swarm Optimization (PSO). This PID controller was validated on a simulated five-story structure based on the Kajima Shizuoka building with five ideal actuators. The effectiveness of the PID controller in reducing the seismic response of the structure with regards to inter-story displacement and acceleration was compared to the uncontrolled response of the structure. It is found that the PID controller with PID parameters obtained from the PSO algorithm offers effective control for the simulated five story structure.more » « less
-
This work investigates traffic control via controlled connected and automated vehicles (CAVs) using novel controllers derived from the linear-quadratic regulator (LQR) theory. CAV-platoons are modeled as moving bottlenecks impacting the surrounding traffic with their speeds as control inputs. An iterative controller algorithm based on the LQR theory is proposed along with a variant that allows for penalizing abrupt changes in platoon speeds. The controllers use the Lighthill-Whitham-Richards (LWR) model implemented using an extended cell transmission model (CTM) which considers the capacity drop phenomenon for a realistic representation of traffic in congestion. The impact of various parameters of the proposed controller on the control performance is analyzed. The effectiveness of the proposed traffic control algorithms is tested using a traffic control example and compared with existing proportional-integral (PI) and model predictive control (MPC) controllers from the literature. A case study using the TransModeler traffic microsimulation software is conducted to test the usability of the proposed controller as well as existing controllers in a realistic setting and derive qualitative insights. It is observed that the proposed controller works well in both settings to mitigate the impact of the jam caused by a fixed bottleneck. The computation time required by the controller is also small making it suitable for real-time control.more » « less
-
The gait patterns of stroke survivors become slow and metabolically inefficient as a result of muscle weakness and low weight-bearing capacity. Exoskeletons and assistive robots can improve gait kinematics and energetics. However, the use of these powered devices may cause a reliance on the device itself that results in limited lasting improvement of the paretic leg function. Specifically, there exists a need to strengthen and train the response of weak ankle muscles, such as the soleus muscle, in stroke survivors. Impaired activation of the soleus muscle induces unnatural gait kinematics and reduced propulsion. The mechanical modulation of the soleus muscle can improve its loading response and enhance gait performance after a stroke. This paper develops a closed-loop feedback controller to manipulate the ankle joint dynamics to mechanically control the soleus muscle response using a motorized ankle orthosis. The control method is inspired by backstepping control techniques and developed to connect the ankle joint angular velocity and the soleus muscle response during the stance phase of walking. The tracking objective is quantified using an integral-like muscle error between the desired soleus response and the actual muscle response, which is measurable using surface electromyography (EMG). The closed-loop electric motor controller is designed to apply ankle perturbations exploiting the backstepping error and an adaptive control term to cope with uncertain parameters that satisfy the linear-in-the-parameters property. A switching signal is developed using heel and toe ground reaction forces to strategically perturb the ankle and target the soleus muscle loading response in real-time during the mid-late stance phase of walking. A Lyapunov-based stability analysis is used to guarantee a globally uniformly ultimately bounded (GUUB) tracking result.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.abo7461
