RH850/C1M-A RDC3A 整数转换器应用指南

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"瑞萨RDC旋变应用笔记主要探讨了如何使用RH850/C1M-A微控制器中的R/D（旋变/数字）转换器（RDC3A），该应用笔记适用于电机控制等应用，详细介绍了旋变传感器的工作原理、RDC3A的基本操作以及如何在实际应用中配置和使用RDC3A。" 本文档首先介绍了RDC3A的主要特性，它作为RH850/C1M-A微控制器的一个组件，用于将旋转变压器（resolver）的模拟信号转换为数字信号，从而便于数字系统处理。旋变是一种用于测量角度位置的传感器，常用于高精度的电机控制系统。 1.1 特性使用：文档中提到了RDC3A的某些关键功能，可能包括高速转换能力、宽动态范围以及对环境干扰的抵抗能力，这些特性使得RDC3A成为电机控制中的理想选择。 2. R/D转换器基础： 2.1 旋变与旋变数字转换器：这部分详细解释了旋变的工作原理，作为一种角位移传感器，它通过两个或三个线圈检测转子相对于定子的位置。接着，RDC3A的作用被阐述，它将旋变产生的正弦和余弦信号转换成数字值，以供微控制器处理。 2.1.1 旋变的使用：旋变能够提供连续的、非接触的角度信息，特别适合在高振动、恶劣环境条件下工作。 2.1.2 旋变的工作机制：通过电磁感应来检测角度变化。 2.1.3 连接旋变与R/D转换器：描述了两者之间的硬件连接方法，包括信号线的布局和电源要求。 2.2 R/D转换器的工作机制： 2.2.1 R/D转换器的概念：解释了R/D转换的基本概念，即从模拟信号到数字信号的转换过程。 2.2.2 R/D转换器的实际操作：详细说明了转换过程，可能包括采样、量化和校准步骤。 2.2.3 设置R/D转换器带宽：讨论了根据应用需求调整转换器带宽的重要性，以优化性能和减少噪声影响。 2.3 附录： 2.3.1 角度处理在电机控制中的注意事项：阐述了在处理电机控制中的角度信息时的一些特殊考虑，如角度的计算和表示方式。 2.3.2 错误发生及其因素：分析了可能导致转换错误的条件和环境因素。 3. 如何使用RDC3A：从3.1 初始化开始，这一部分提供了实际应用中配置和使用RDC3A的步骤，可能涵盖了初始化设置、参数配置、错误处理和调试技术。这篇应用笔记不仅提供了理论背景，还包含了许多实用的工程指导，是开发使用RH850/C1M-A和RDC3A进行旋变传感器数据处理的工程师的重要参考资料。通过深入理解这些内容，工程师可以有效地集成和优化RDC3A在各种电机控制应用中的性能。

RH850/C1M-A R/D Converter (RDC3A)

R01AN4051EJ0211 Rev.2.11 Page

of 44

July.6.22

ε is the control deviation in this control loop. The negative feedback control provides feedback so that the

control deviation becomes 0. When θ = Φ, the analog angle information from a resolver has been converted

to the digital angle Φ.

Sets the response speed with the PI compensator in a loop.

2.2.3 Setting the R/D Converter Bandwidth

The bandwidth of the PI compensator needs to be set when an R/D converter is used. The bandwidth is

expressed by the frequency. When the frequency is set high, the response becomes quick but has a large

influence by noise and other factors. On the other hand, when the frequency is set low, the response

becomes slow and immune to noise and the R/D converter output becomes stable. For an R/D converter

mounted on the Renesas MCU, the default is 800Hz and can be changed.

Some R/D converters have a function to set the bandwidth automatically. When this function is used, the

bandwidth is set low when the resolver is stable and it is set high automatically when the quick response is

required such as at acceleration. The R/D converters mounted on the Renesas MCU have an auto-adjusted

function.

The bandwidth setting of an R/D converter has influence on response speed for acceleration and angle step

but has no influence on the maximum speed of when a resolver is rotating stationary. For example, when the

bandwidth is set low (around 200Hz), if a resolver is slowly accelerated, it can be tracked even the final

speed is high (for example 1000Hz=60000rpm). Also, when a resolver is rotating stationary at high speed,

inside an R/D converter remains stationary (ε is small) and the bandwidth is set low in auto-adjusted.

Figure 2.7 Output Change by the Bandwidth Change of PI Compensator shows the difference in output

by the bandwidth of PI compensator setting.

Figure 2.7 Output Change by the Bandwidth Change of PI Compensator

RH850/C1M-A R/D Converter (RDC3A)

R01AN4051EJ0211 Rev.2.11 Page

of 44

July.6.22

2.3 Appendix

2.3.1 The Handling of Angles in the Motor Control

In the brushless DC motor control, the input voltage into a motor is varied according to the shaft angle of a

motor.

It should be noted that the mechanical shaft angle of a motor (mechanical angle), the output angle of a

resolver (resolver angle) and the angle which determines the voltage applying to a motor (electrical angle)

are not always equal depending on number of poles. The definitions of terms in this document are as follows.

• Mechanical angle The mechanical shaft angle of a motor

• Resolver angle The angle output from an R/D converter

• Electrical angle The angle which determines the voltage applying to a motor

• The number of resolver poles The ratio of mechanical angle to resolver angle (mechanical angle :

resolver angle=1 : the number of resolver poles)

• The number of motor pole pairs The ratio of mechanical angle to electrical angle (mechanical angle :

electrical angle=1 : the number of motor pole pairs)

Example : When the number of resolver poles is 2, the number of motor pole pairs is 4.

When the mechanical shaft rotates once, the resolver angle rotates twice and the voltage to the motor

rotates 4 times. In this case, the controller device doubles the resolver angle (number of motor pole

pairs/number of resolver poles) and calculates the applied voltage to the motor. The number of poles

needs to be considered for the angular offset.

The reason for increasing the number of motor pole pairs in the brushless DC motor is because it enables to

increase the torque(rotation power of the motor). Since the number of poles of the VR resolver is more than

2, the mechanical angle, the electrical angle and the resolver angle are usually not equal. On the other hand,

when the number of resolver poles and the number of motor pole pairs are same, the electrical angle and the

resolver angle become equal.

Figure 2.8 shows an example of the angular relation when the number of resolver poles =2, the number of

motor pole pairs=4.

Figure 2.8 Pole and the Angle of the relationship

When the number of resolver poles is large, the absolute value of the mechanical angle can not be

determined.(The mechanical angle X degree and X + 180degree can not be distinguished.)

For the motor control, the relative angle can be used for the rotation control as long as the number of motor

pole pairs >= the number of resolver poles. For the VR resolver, the number of poles is always more than 2

because of its mechanism.

Shape of rotors

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