Magnetic Actuation for Full Dexterity Microrobotic Control Using Rotating Permanent Magnets

这篇文章主要描述了一个基于8旋转永磁铁的5自由度驱动系统，没有任何移动部件，增加了安全性，减少了发热，而且廉价。可以产生所需的3D场和3D场梯度。（对于只有一个内置磁铁胶囊来说，只能在它身上产生5D控制）

使用旋转永磁体的用于完全灵巧微机器人控制的磁驱动
Magnetic Actuation for Full Dexterity Microrobotic Control Using Rotating Permanent Magnets [1]
Paper Link
Authors: Ryan, Patrick, etc.
2019, IEEE Transactions on Robotics (T-RO)

0. 摘要 Abstract

这篇文章展示一个新型驱动系统，它使用一个旋转永磁体阵列来产生相同级别的对无绳微尺度设备的控制，并有产生增大的磁场和梯度强度和最小的热能产生的潜力。与以前的永磁体驱动系统不同的是，这里所提出的系统不需要控制磁铁的任何危险的移动运动，导致是一个简单，安全和廉价的系统。所展现出来的概念验证原型机系统，它有八个永磁铁，能在任何方向产生场和场梯度，可变化的大小分别在0到30mT和0.83T/m之间。
This paper presents a new type of actuation system, which uses an array of rotating permanent magnets to generate the same level of control over untethered microscale devices with the potential of increased magnetic field and gradient strength and minimal heat generation. In contrast with perivous permanent-magnet actuation systems, the system proposed here does not require any hazardous translational motion of control magnets, resulting in a simple, safe and inexpensive system. The proof-of-concept prototype system presented, with 8 permanent magnets, can create fields and field gradients in any direction, with variable magnitudes between zero and 30mT and 0.83T/m, respectively.

1. 介绍 Introduction

不像一个机器人操纵单磁铁系统，所提出的系统包含多个永磁铁，每一个有能力被旋转，与其他磁铁独立。
Unlike a robotically manipulated single magnet system, the proposed system is composed of multiple permanent magnets, each with the ability to be rotated independently of the other magnets.

2. 使用旋转型永磁铁的控制 Control using rotatable permanent magnets

驱动系统的输入是所有驱动磁铁的电机角度$\theta =[\begin{array}{cccc}{\theta }_1& {\theta }_2& \cdots & {\theta }_N\end{array}{]}^T$。我们控制输入作为非线性优化问题的一个解：
The control inputs to the actuation system are the motor angles of all the actuator magnets $\theta =[\begin{array}{cccc}{\theta }_1& {\theta }_2& \cdots & {\theta }_N\end{array}{]}^T$. We find the control inputs as a solution to the nonlinear optimization problem:

$$arg\underset{\theta }{\min }f=K||\mathbf{B}(\theta )-{\mathbf{B}}_0|{|}^2+(1-K)||\mathbf{F}(\theta )-{\mathbf{F}}_0|{|}^2$$

其中${\mathbf{B}}_0$和${\mathbf{F}}_0$分别是期望场和力输出；$\mathbf{B}(\theta )$和$\mathbf{F}(\theta )$分别是在一组给定电机角度下产生的场和力向量；$K$是用来权衡等式的两半来解决场和力的测量单位之间的差异，其中$0<K<1$。用于选择$K$的一个理论包含最大场和力，分别表示为$B_{max}$和$F_{max}$。设置$K$等于$\frac{B_{max}^{-2}}{B_{max}^{-2}+F_{max}^{-2}}$平衡场和力部分基于理论最大系统输出。
Where ${\mathbf{B}}_0$ and ${\mathbf{F}}_0$ are the desired field and force outputs, respectively; $\mathbf{B}(\theta )$ and $\mathbf{F}(\theta )$ are the field and force vectors that are produced for a given set of motor angles; $K$ is used to weigh the two halves of the equation to account for the difference in the units of measurements for the field and force, where $0<K<1$. One method for choosing $K$ involves the maximum field and force, donated as $B_{max}$ and $F_{max}$, respectively. Setting $K$ equal to $\frac{B_{max}^{-2}}{B_{max}^{-2}+F_{max}^{-2}}$ balances the field and force components based on the theoretical maximum system output.

[1]: Ryan, Patrick, and Eric Diller. “Magnetic actuation for full dexterity microrobotic control using rotating permanent magnets.” IEEE Transactions on Robotics 33.6 (2017): 1398-1409.