J. Mike Walker '66 Department of Mechanical Engineering, Texas A&M University 3123 TAMU, College Station, Texas 77843, USA.
Rev Sci Instrum. 2023 Jul 1;94(7). doi: 10.1063/5.0152691.
This paper presents a novel positioning feedback sensor using a pair of Hall effect elements on a long-range flexure stage. The proposed Hall effect positioning feedback sensor eliminates error and uncertainty by measuring the center of the flexure stage, where a machine tool or measurement probes would take place in the industrial application. A pair of Hall effect elements were amplified in a differential configuration as the cylindrical permanent magnet enclosed in the center of the shuttle in the flexure stage that moves back and forth, generating a uniform gradient magnetic flux intensity. Nonlinear magnetic flux characteristics of a single Hall effect element were eliminated, and high-quality sensor sensitivity was achieved by differential amplification of the two Hall effect elements. The magnetic field analysis to characterize the linearity of the proposed displacement sensor was simulated using the finite element method to prove that the non-linearity of a single hall effect element may be mitigated by employing the differential amplification technique. The flexure stage was additively manufactured into a monolithic structure, and the permanent magnet was fitted into the shuttle of the flexure stage. Each Hall effect element was placed on either side of the magnet at a certain distance on the axis of shuttle movement. The proposed sensor was characterized by performing dynamic system identification of the flexure stage: open-loop response and closed-loop response. The Laser Displacement Sensor (LDS) with the 10 nm resolution was used for baseline comparison and datum line with respect to the proposed sensor. The proposed sensor responses agreed well with LDS in various dynamic inputs. The sensor response was analyzed with two differential amplification signal processing techniques. The maximum sensitivity of the two signal processing techniques was determined to be 16.55 mV/μm, and the resolution was observed as 2.5 μm. In sum, the differentially amplified Hall effect displacement sensor achieved positioning feedback with high sensitivity and linearity and minimized the sensor placement error while maintaining low cost and simple configuration.
本文提出了一种新颖的定位反馈传感器，该传感器使用长行程挠性台上的一对霍尔效应元件。所提出的霍尔效应定位反馈传感器通过测量挠性台的中心来消除误差和不确定性，在工业应用中，机床或测量探头将位于该中心。一对霍尔效应元件以差分配置进行放大，因为在挠性台的梭子中心封装了一个圆柱形永磁体，该永磁体在挠性台内前后移动，产生均匀的梯度磁场强度。通过对两个霍尔效应元件进行差分放大，消除了单个霍尔效应元件的非线性磁通量特性，从而实现了高质量的传感器灵敏度。使用有限元法对磁场进行分析，以模拟所提出的位移传感器的线性度，证明通过采用差分放大技术可以减轻单个霍尔效应元件的非线性。挠性台采用增材制造技术制成整体式结构，永磁体安装在挠性台的梭子中。每个霍尔效应元件都放置在磁铁的两侧，在梭子运动轴线上有一定的距离。通过对挠性台进行动态系统识别，对所提出的传感器进行了特性描述：开环响应和闭环响应。分辨率为 10nm 的激光位移传感器（LDS）用于基线比较和相对于所提出的传感器的基准线。在各种动态输入下，所提出的传感器的响应与 LDS 吻合良好。对传感器响应进行了两种差分放大信号处理技术的分析。两种信号处理技术的最大灵敏度确定为 16.55 mV/μm，分辨率观察到为 2.5μm。总之，差分放大的霍尔效应位移传感器实现了具有高灵敏度和线性度的定位反馈，同时最小化了传感器的放置误差，同时保持低成本和简单的配置。
