## 人工智能+车：开源的自动驾驶系统——Openpilot

openpilot 是 comma 公司开源的一个自动驾驶辅助系统，包含 软件 和 硬件 两部分，其中软件和第一代硬件都是开源的，可以在 github 上找到。

### Openpilot 的主要特性包括哪些？

Openpilot 官方版本支持 车道保持 、ACC巡航自动辅助变道

ACC巡航：检测前车、障碍物，根据前车速度调节车速（油门、刹车），与前车保持安全距离。

• 0.6.4 之后的版本在测试过程中发现，如果没有车道线情况下，会跟随前车轨迹行驶

# Track switching for a magnetically levitated transportation system and method

Abstract
A magnetically levitated transportation system employs permanent magnet rails along a guideway that interact with permanent magnets on a vehicle. The rails are optimized to reduce magnetic mass and cost of materials, while maximizing lift force. The vehicle is stabilized in the lateral and yaw directions with feedback controlled lateral control coils that interact with the permanent magnet rails on the guideway. A track switching structure employs permanent magnet rails that gradually widen along a segment of track and separate into two identical diverging rails. Feedback controlled lateral control coils in a moving vehicle stabilize that vehicle over one or the other pairs of diverging rails, as directed by a control computer, thereby causing the vehicle to continue along one path or the other, with no moving or active elements required in the track.

### Images (11)

Classifications
B60L13/003 Crossings; Points

## 飞行：电磁悬浮四轴飞行（器）

Obviously this “quadcopter” is a demonstration device, showing how moving magnets over a conducting surface can generate levitation. It has not been optimized to minimize losses or be an efficient mode of transport. I still think it’s pretty cool. I’m used to seeing light things levitated by induced currents but not a 100+ lb machine.

# 声能

$W=W_{\mathrm {potential} }+W_{\mathrm {kinetic} }=\int _{V}{\frac {p^{2}}{2\rho _{0}c^{2}}}dV+\int _{V}{\frac {\rho _{0}v^{2}}{2}}dV$

• $$V$$ – 流体的体积
• $$p$$ – 声压
• $$v$$ – 流体质点速度
• $$\rho_0$$ – 流体静态密度
• $$c$$ – 声速

## 声能密度

$\epsilon ={\frac {p^{2}}{2\rho _{0}c^{2}}}+{\frac {\rho _{0}v^{2}}{2}}$

## 平均声能量密度

${\bar {\epsilon }}={\frac {p_{e}^{2}}{\rho _{0}c^{2}}}$

## 参考

1.  L. E. Kinsler, A. R. Frey, A. B. Coppens, and J. V. Sanders, 1999. Fundamentals of Acoustics, fourth edition (Wiley).第5.8节。
2. ^ 杜功焕、朱哲明、龚秀芳，声学基础，第二版，第4.7节。