【作者】 李博；

【导师】 魏廷存；

【作者基本信息】 西北工业大学 ， 计算机科学与技术， 2017， 博士

【摘要】 电容式多点触摸传感技术,因具有优异的人机交互用户体验,已在各种智能显示终端中获得广泛应用。在移动通讯和消费电子等应用领域,要求电容式多点触摸传感技术具有低功耗和低成本的特点,以提高电池的续航能力和市场竞争力。而在汽车电子、商业办公、工业控制等领域,要求电容式多点触摸传感技术具有响应速度快和抑制噪声能力强等特点。本论文利用触摸信息的稀疏性特点,提出了基于信息选择的传感系统设计新思路。通过对触摸信息进行选择性采集和处理,显著减小了数据采集和处理规模,降低了系统的硬件和软件设计复杂度,可实现低成本和低功耗的信息感知。同时,由于数据采集和处理规模显著减少,提升了系统的响应速度和可靠性优化空间。论文的主要研究工作和创新点如下。(1)针对现有电容式多点触摸传感系统存在的数据采集量较大、系统成本和功耗较高、性能优化空间受限的问题,提出了具有多维度观测和选择性信息采集特征的触摸预测和窗口采样(Touch Prediction and Window Sensing,TPWS)策略,以及采用线扫描和点扫描的TPWS系统实现方案。TPWS系统首先采用组合观测方法获得有效信息命中概率高、空间分辨率低的预采样数据,通过简单的数据处理实现触摸信息的低成本粗略估计。接着,基于触摸信息的粗略估计结果,采用局部观测方法对估计的可能触摸区域进行选择性信息采集,获得具有较高空间分辨率和较高有效信息命中概率的局部采样数据,然后通过对局部采样数据处理实现触点位置的像素级坐标估计。与现有技术相比,TPWS系统的数据采集和处理规模大幅度降低,检测效率显著提高。理论分析结果表明,对于15英寸触摸屏,TPWS系统相比传统系统的检测效率在单点触摸时最大可提高20倍。(2)针对TPWS系统线测量和点测量时输入信号范围大且不确定的特点,提出了采用电容桥再平衡方法的触摸信号测量技术,以及采用该技术的数字化前端读出电路结构。传统的前端读出电路使用电荷积分器等模拟电路实现触摸信号的线性转换,容易出现输出失真以及难以同时兼顾高测量精度和大测量范围等问题。本文采用电容桥再平衡的测量技术,使用电压比较器作为触摸信号转换的前端,系统的测量精度仅取决于补偿电容器的最小调节步长以及电压比较器的最小分辨电压,系统的测量范围仅取决于补偿电容的大小,通过设计适当的补偿电容调节步长和范围以及比较器的精度,可以保证系统具有较高的测量精度和较大的测量范围,消除了传统模拟测量系统的输出失真问题。本文设计实现了一款适用于TPWS系统的数字化前端读出电路芯片,该芯片具有10位分辨率,27fF最小电容分辨精度,最大13.824pF测量输入范围,单个通道面积仅为0.087mm~2,在较小芯片面积上兼顾了系统测量范围和测量精度的需求。将该芯片应用于一个15寸的触摸屏系统,系统扫描帧率大于83Hz,动态电流消耗小于每测量单元6μA,与现有技术相比,采用TPWS策略的系统在功耗和成本方面都具有明显优势。(3)为了提高TPWS系统的抗干扰能力和响应速度,提出了全驱动差分线测量和差分点测量方法。为了消除显示噪声和开关电源噪声对检测精度的影响,提出了正向并行驱动和负向并行驱动相结合的差分线测量和差分点测量方法,实现了低噪声的信号采集。通过采用全驱动技术,减小了驱动信号在传感器电极上传播时的RC延迟,提高了信息采集速度。本文设计实现了一款基于TPWS策略的低噪声高速度数字化前端读出电路芯片,测试结果表明,采用上述技术后,信噪比从26dB提高至35dB,扫描帧率从83Hz提高到120Hz,系统的信噪比和响应速度均得到显著提升。本论文提出的多维度观测和选择性信息采样方法对于信息稀疏型阵列式传感器的信号采样和处理研究具有一定的理论意义,对于研发电容式多点触摸信息传感系统具有重要的工程实用价值。更多还原

【Abstract】 The capacitive multi-touch sensing technique,due to its excellent user experiences in the human-machine interaction(HCI),has been widely used in the smart display terminals.On one hand,the capacitive multi-touch sensor system should be low power and low cost in the application of mobile communication and consumer electronics due to the limited battery capacity and the required market competitiveness.On the other hand,fast respond speed and good noise suppression are required in the application of automotive electronics,commercial office,industrial control terminal and so on.This dissertation utilizes the sparsity of the touch information,and proposed a new idea for designing the capacitive multi-touch sensing system based on information selection.The data sampling and processing scale are notably reduced due to the selective sampling of the touch information,and then the hardware and software design complexity is also reduced.Consequently,the system cost and power dissipation are decreased.In addition,the system respond speed is increased and the possibility of reliability optimization is provided.The main innovations and researches in this dissertation are summarized as follows.(1)Considering the issues existed in the traditional capacitive multi-touch sensing systems,such as large amount of sampling data,high system cost and power dissipation,and the limitations in the further performances optimization,the touch prediction and window sensing(TPWS)strategy is proposed which is characterized by multi-dimension observation and selective sampling,and the realization scheme of the TPWS strategy using the combination of point scanning and line scanning is also proposed.Firstly,the pre-sampling data with higher information hit rate and lower spatial resolution are obtained by combined information observation,and then the possible touch regions are roughly estimated with low cost by simple data processing.Secondly,based on the above rough sensing results,the estimated possible touch regions are selected and sampled,and then the sampled information of these local regions,which have higher spatial resolution and higher information hit rate,are acquired.Consequently,the pixel level coordination of the touch positions can be derived by processing the sampled data of these local regions.Since the signal sampling and data processing scale is notably decreased for the TPWS strategy,the sensing efficiency of system is obviously increased comparing with the existed techniques.According to the theoretical analysis,for a 15-inch touch panel with one touch,the sensing efficiency of TPWS system could be increased by 20 times as compared with the traditional multi-touch system.(2)Considering the large and uncertain input signal range required by the TPWS strategy during the measurements with point and line scanning,a new touch signal measurement technique based on the rebalance of Capacitance Bridge is proposed,and a digital front-end readout circuit structure based on the measurement technique is constructed.Traditional front-end readout circuits employ analog circuit including charge integrators for transforming the touch signal to electronic signal linearly,and thus it is very difficult to realize simultaneously a large input range and high precision measurement without distortion.This dissertation adopts a schema of the rebalance of Capacitance Bridge,and a voltage comparator is used for the signal measurement.The measurement precision depends on the minimal variation step of a complementary capacitance and the voltage discrimination of the comparator.The measurement range relies on the value of the complementary capacitance.A high precision and large input measurement system without any distortion can be realized by designing adequate variation step and value of the complementary capacitance and a high precision comparator.A prototype chip of the digital front-end readout circuit is designed and implemented.The quantization resolution is 10 bits,the discrimination of capacitance is 27fF,the maximum input capacitance could be 13.824pF,and the die size per sensing channel is only 0.087 mm~2.In one word,both the large measurement range and high measurement precision are realized with a small die size.A15-inch capacitive multi-touch screen system is realized with the prototype chips.The sensing frame rate of the prototype system is over 83Hz.The dynamic current is less than 6μA per sensing cell.Compared with the existed techniques,the TPWS system is with extremely low power dissipation and low system cost.(3)In order to increase the noise suppression ability and the response speed of the TPWS system,the differential point and line measurements method with fully-driving is proposed.In order to decrease the influences of the display noise and the power switching noise on measurement precision,the differential line measurement and differential point measurement methods with the combination of parallel positive and negative driving are developed,and the low noise signal sampling is realized.Moreover,fully-driving methods are adopted for reducing the RC delay during signal transmission on the sensor electrodes,and thus the signal sampling speed is increased.A low noise and high speed digital front-end readout chip based on the TPWS strategy is designed and implemented.The test results demonstrate that the signal to noise ratio is improved from 26 dB to 35 dB,and the sensing frame rate is increased from 83 Hz to 120 Hz by adopting the above techniques.So,both the signal to noise ratio and the response speed of the TPWS system are improved obviously.The multi-dimension observation and the selective information sampling method proposed in this dissertation can be also used in the signal sampling and processing for the other arrayed sensor with sparse information.And the research and design results in this dissertation have important engineering practical value for developing capacitive multi-touch sensor system.更多还原