Patent Publication Number: US-2005131617-A1

Title: Data collecting system and data transmitting method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a data collecting system for collecting data which are outputted from plural data processing devices.  
      2. Description of Related Art  
      When data detected by plural sensors are transmitted to a data analyzing device so as to be analyzed, generally, a data collecting system is configured by connecting plural data outputting devices for outputting the data detected from the sensors and the data analyzing device to a common bus. In that case, the data analyzing device serves as a host, and individually obtains the data from each data outputting device by designating each data outputting device on the basis of addresses and the like. Therefore, the plural data outputting devices transmit the data by an interrupting process under control of the data analyzing device so that the data analyzing device obtains the data from the plural data outputting devices in real time.  
      Therefore, it is required that the respective data outputting devices extract the data detected from the sensors and transmit the detected data by the interrupting process. For example, when an analog sensor is used as the sensor, since the data outputting device has to A/D-convert an analog detecting signal, which is outputted from the sensor, and transmit it, process loads required to the respective data outputting devices become large. In addition, when one data outputting device A/D-converts analog detected data from the sensor during the transmission of the data from another data outputting device to the data analyzing device, it can happen that accuracy of A/D conversion is problematically reduced by a noise caused by the transmission of the data by another data outputting device.  
      There is a method of transmitting data by so-called cascade connection or daisy chain connection, not by the above-mentioned connection of the plural data outputting devices to the common bus. This method is disclosed in Japanese Patent Application Laid-open under No. 2001-145093 and No. 2001-251609.  
     SUMMARY OF THE INVENTION  
      The present invention has been achieved in order to solve the above problems. It is an object of this invention to provide a data collecting system, whose configuration is simple, capable of effectively collecting plural data without an effect of a noise due to communication.  
      According to one aspect of the present invention, there is provided a data collecting system which includes a data collecting device and plural data processing devices connected to the data collecting device by a cascade connection, each of the data processing devices sharing repeated data processing period and communication period with each other, individually executing a data process in the data processing period, and adding data obtained by the data process in the communication period to a data transmitting signal received from the preceding data processing device, to transmit it to the subsequent data processing device.  
      Each of the data processing devices individually executes an A/D conversion and other data process, for example, and adds the data obtained by the data process to the data transmitting signal to transmit it to the subsequent cascade-connection data processing device in sequence. More concretely, the data processing device at the head of the cascade connection periodically transmits starting information of the data transmitting period and starting information of a data processing period in order to prescribe the data processing period and the communication period of the whole data collecting system.  
      At that time, the data transmitting signal includes the data processing period and the communication period. In the data processing period, all the data processing devices execute the data process, and never transmit the data to the subsequent data processing devices. Thereby, it can be prevented that a noise caused by the transmission of the data puts an adverse effect on the data process in all the data processing devices. On the other hand, in the communication period, the respective data processing devices transmit the data obtained by the data process in sequence. Therefore, the respective data processing devices can execute the data process without the effect of the noise, and can efficiently transmit a result thereof to the data collecting device.  
      If the data processing period in the data transmitting signal is set to be longer than a maximum data processing time by the plural data processing devices, all the data processing devices can start transmitting the data in the communication period after individually completing the data process.  
      In addition, the communication period in the data transmitting signal may include an individual communication period assigned to each of the plural data processing devices. Since each of the data processing devices transmits the data in the individual communication period assigned to its data processing device, the data collecting device can correctly discriminate the data which are transmitted from the plural data processing devices. By continuously assigning the individual communication period within the communication period, the communication period can be used efficiently.  
      In a preferred embodiment, each of the data processing devices may include an A/D converter which executes A/D conversion as the data process. More concretely, each of the data processing devices may be connected to an analog sensor, and may A/D-convert an analog detecting signal which is outputted from the analog sensor as the data process. Since the data is not transmitted during the A/D converting process in each of the data processing devices, it can be prevent that accuracy of A/D conversion is decreased due to a noise caused by the data transmission.  
      In addition, it is preferable that the data processing device at the head of the cascade connection periodically transmits the data transmitting signal with a cycle longer than a total of the data processing period and the communication period. Thereby, the data collecting system can periodically obtain accurate data from each of the data processing devices.  
      According to another aspect of the present invention, there is provided a data transmitting method which is executed among plural cascade-connection data processing devices, the data processing device at a head of the cascade connection generating a data transmitting signal including a data processing period and a communication period, and transmitting it to the subsequent data processing device, and each of the data processing devices executing a data process in the data processing period, and transmitting data obtained by the data process to the subsequent data processing device in the communication period based on the data transmitting signal. By the data transmitting method, identically to the above-mentioned data collecting system, a data process can accurately be executed in each of the data processing devices, and the data can effectively be transmitted to other devices.  
      The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram schematically showing a configuration of a robot arm controlling system to which a data collecting system according to an embodiment of the present invention is applied.  
       FIGS. 2A and 2B  are block diagrams showing an inside configuration of a data processing device shown in  FIG. 1 .  
       FIGS. 3A  to  3 E are timing charts showing data transmitting signals among data processing devices. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The preferred embodiments of the present invention will now be described below with reference to the attached drawings.  FIG. 1  schematically shows a configuration of a robot arm controlling system to which a data collecting system according to an embodiment of the present invention is applied.  
      In  FIG. 1 , a robot arm controlling system  100  controls positions of plural robot arms, and controls three robot arms  24   a  to  24   c  in the present embodiment. Namely, as shown in  FIG. 1 , the robot arm controlling system  100  includes data processing devices  10   a  to  10   c , sensors  22   a  to  22   c , the robot arms  24   a  to  24   c , actuators  26   a  to  26   c , a data collecting/analyzing device  2  and a controller  3 .  
      The positions of the respective robot arms  24   a  to  24   c  are controlled by the actuators  26   a  to  26   c  which use air pressure, for example. The respective actuators  26   a  to  26   c  are controlled by the controller  3 .  
      The positions of the robot arms  24   a  to  24   c  are detected by the sensors  22   a  to  22   c , respectively. In the present embodiment, the respective sensors  22   a  to  22   c  are configured as analog sensors for detecting the positions of the robot arms  24   a  to  24   c , and output analog detecting signals indicating the detected positions of the robot arms  24   a  to  24   c  to the respective data processing devices  10   a  to  10   c.    
      The data processing devices  10   a  to  10   c  A/D-convert the analog detecting signals indicating the positions of the robot arms  24   a  to  24   c  which are supplied from the sensors  22   a  to  22   c , and output them as digital detecting signals.  
      The data processing devices  10   a  to  10   c  are connected to the data collecting/analyzing device  2  by a serial connection system which is generally called “cascade connection” or “daisy chain”. Namely, the data processing device  10   a  which is located at the head of the cascade connection supplies a data transmitting signal Sa to the subsequent data processing device  10   b , and the data processing device  10   b  supplies a data transmitting signal Sb to the further subsequent data processing device  10   c . The data processing device  10   c  supplies a data transmitting signal Sc to the data collecting/analyzing device  2 .  
      The data processing devices  10   a  to  10   c  add digital detecting signals Da to Dc corresponding to the sensors  22   a  to  22   c  to the data transmitting signals Sa to Sc respectively, and transmit them to the subsequent data processing apparatus  10  or the data collecting/analyzing device  2 , though the detail will be explained later. In such the method, the digital detecting signals Da to Dc corresponding to the sensors  22   a  to  22   c  are collected and analyzed by the data collecting/analyzing device  2 . In the present embodiment, the data collecting/analyzing device  2  analyzes the positions of the respective sensors  22   a  to  22   c  on the basis of the collected digital detecting signals Da to Dc, and outputs, to the controller  3 , position controlling quantities of the respective robot arms  24   a  to  24   c  in accordance with the result. The controller  3  drives the respective actuators  26   a  to  26   c  on the basis of the position controlling quantities of the respective sensors  22   a  to  22   c  which are obtained from the data collecting/analyzing apparatus  2 , and controls the positions of the respective robot arms  24   a  to  24   c . In the present embodiment, the positions of the robot arms  24   a  to  24   c  are feedback-controlled in such the method. Such the position control, by detecting the digital detecting signals Da to Dc and collecting the data to analyze it, is repeatedly and periodically executed.  
      Next, the description will be given of inside configurations of the data processing devices  10   a  to  10   c .  FIG. 2A  shows the inside configuration of the data processing apparatus  10   a  located at the head of the cascade connection, and  FIG. 2B  shows the inside configuration of the data processing devices  10   b  and  10   c  located at positions subsequent to the data processing apparatus  10   a.    
      As shown in  FIG. 2A , the data processing device  10   a  includes an A/D converter  16 , a communication unit  14  and a CPU  12  for control. The A/D converter  16  A/D-converts the analog detecting signal which is supplied from the sensor  22   a , and generates the digital detecting signal Da. The CPU  12  generates data transmitting signals for transmitting the digital detecting signals Da to Dc through the cascade-connection data processing devices  10   a  to  10   c , and adds the digital detecting signal Da to the data transmitting signal as the need arises. The communication unit  14  transmits the data transmitting signal to the subsequent data processing device  10   b  under the control of the CPU  12 .  
      On the other hand, as shown in  FIG. 2B , each of the subsequent data processing devices  10   b  and  10   c  includes the CPU  12 , the communication unit  14 , a communication unit  15  and the A/D converter  16 . Namely, each of the data processing devices  10   b  and  10   c  includes the communication unit  15  for performing communication with the data processing device  10   a  or  10   b  located at the upstream position of the cascade connection in addition to the configuration of the data processing device  10   a.    
      Identically to the data processing device  10   a , the A/D converter  16  A/D-converts the analog detecting signal which is supplied from the correspondent sensor  22   b  or  22   c , and generates the digital detecting signal Db or Dc. The communication unit  15  receives the data transmitting signal Sa or Sb from the preceding data processing device  10   a  or  10   b . The CPU  12  adds, to the data transmitting signal Sa or Sb, the digital detecting signal Db or Dc generated by the A/D converter  16 , and supplies it to the communication unit  14 . The communication unit  14  outputs the data transmitting signal Sb or Sc. It is noted that the data processing device  10   b  supplies the data transmitting signal Sb to the subsequent data processing device  10   c , and the data processing device  10   c  supplies the data transmitting signal Sc to the data collecting/analyzing device  2 .  
      Next, the description will be given of details of a method of transmitting the data among the plural cascade-connection data processing devices  10   a  to  10   c , with reference to  FIGS. 3A  to  3 E.  FIGS. 3A  to  3 E are timing charts showing the data transmitting signals which are communicated among the data processing devices  10   a  to  10   c . In  FIGS. 3A  to  3 E, the data transmitting signals outputted from the data processing devices  10   a ,  10   b  and  10   c  are indicated as Sa, Sb and Sc, respectively, identically to those shown in  FIG. 1 .  
      In the present embodiment, the data processing device  10   a  located at the head of the cascade connection generates the data transmitting signal. The present invention is characterized in that the data transmitting signal includes a data processing period Tp and a communication period Tdt, as shown in  FIGS. 3A  to  3 E. In the data processing period Tp, the respective data processing devices  10   a  to  10   c  execute the data process, and do not communicate (transmit) the data. Namely, the data processing period Tp is set as a period in which the respective data processing devices execute only the data process. In the present embodiment, the data process is an A/D converting process of the analog detecting signal by the A/D converter  16 . Like this, the data processing devices  10   a  to  10   c  share the data processing period Tp and the communication period Tdt, and the data processing period Tp and the communication period Tdt are periodically and repeatedly executed.  
       FIG. 3A  shows a waveform of data transmitting signal outputted from the respective data processing devices  10   a  to  10   c  in the data processing period Tp. Since outputting the data from the respective data processing devices  10   a  to  10   c  is inhibited in the data processing period Tp, output data is not included at the position corresponding to the communication period Tdt.  
      Like this, by providing the data processing period Td dedicated to only the data processing, in which the respective data processing devices  10   a  to  10   c  do not transmit the data and only individually execute the data process, in the data transmitting signals S, it can be prevented that a noise which may occur due to the data communication affects the data process in the respective data processing devices. For example, as for the A/D conversion in the present embodiment, if a certain data processing device executes the data communication during the A/D converting process of anther data processing device, the effect of the noise caused by the data communication is given to the A/D converting process, and accuracy of the A/D conversion sometimes decreases. Like the present embodiment, when a subject of the A/D converting process as the data process is the analog detecting signal of the sensor  22 , a detected quantity may change by the effect of the noise due to the communication, and an adverse effect is given to the control of the whole system. In this point, as described above, if the data processing period Tp is provided and all the data processing devices never execute the communication in the period, the data process can be executed in the respective data processing devices with high accuracy.  
      Therefore, the data processing period Tp is set to be longer than the longest necessary time of the data processes executed in the plural data processing devices  10   a  to  10   c . Thereby, it can be prevented that the data communication is started before all the data processing devices individually complete the data process.  
      On the other hand, the communication period Tdt is set as a period in which the respective data processing devices  10   a  to  10   c  transmit the data in sequence. The communication period Tdt includes individual communication periods Ta to Tc, which are assigned to the respective data processing devices  10   a  to  10   c , and a margin period Tm. Though the communication period Tdt is dedicated to the data transmission, if the respective data processing devices  10   a  to  10   c  transmit the data in disorder, the data collecting/analyzing device  2  cannot identify from which data processing device the received data is transmitted. Therefore, the individual communication periods Ta to Tc are set in the communication period Tdt. Namely, it is prescribed that the data processing devices  10   a  to  10   c  transmit the data during the individual communication periods Ta to Tc, respectively. Thereby, the data collecting/analyzing device  2  can regard the data transmitted□@in each individual communication period as the data which is transmitted from the data processing device  10  corresponding to the individual communication period.  
       FIGS. 3B  to  3 D schematically show data contents of the data transmitting signals Sa to Sc which are outputted from the respective data processing devices  10   a  to  10   c  in the communication period Tdt. The data transmitting signal Sa outputted from the data processing device  10   a  includes the digital detecting signal Da, and the digital detecting signal Db is added to the data transmitting signal Sb outputted from the data processing device  10   b . The digital detecting signal Dc is further added to the data transmitting signal Sc outputted from the data processing device  10   c . In addition,  FIG. 3E  shows an example of a waveform of the data transmitting signal Sc shown in  FIG. 3D .  
      The lengths (time widths) of the respective individual communication periods Ta to Tc are determined in accordance with the quantities of the data which are outputted from the respective data processing devices. Namely, a long individual communication period is given to the data processing device having a large output data quantity, and a short individual communication period is given to the data processing device having a small output data quantity. When data transmitting speed is constant, the length (time width) of the individual communication period is prescribed by the quantity of the data to be transmitted.  
      As a method of setting the individual communication period, first the time width (transmission data quantity) of the correspondent individual communication period device may be determined on the basis of the output data quantity from each data processing, and may be set in the communication period Tdt in sequence. For example, if it is assumed that the output data quantities from the data processing devices  10   a  and  10   b  are 12 bits respectively and the output data quantity from the data processing device  10   c  is 16 bits, a period from starting time t1 of the communication period Tdt to a period corresponding to the data quantity 12 bits, i.e., time t2, may be set to the individual communication period Ta, and a period from starting time t2 to a period corresponding to the data quantity 12 bits, i.e., time t3, may be set to the individual communication period Tb. Moreover, a period from time t3 to a period corresponding to the data quantity 16 bits, i.e., time t4, may be set to the individual communication period Tc. Like this, by setting each individual communication period, each of the data processing devices  10   a  to  10   c  adds its output data (each of the digital detecting signals Da to Dc) within the correspondent individual communication period in the communication period Tdt of the data transmitting signal S in sequence, and transmits the data to the data processing device at the downstream position. Finally, the output data from all the data processing devices is transmitted to the data collecting/analyzing device  2  through the cascade connection. The margin period Tm is set for the purpose of a stable execution of a data transmitting process.  
      It is preferable that the plural individual communication periods are continuously set on a time axis (i.e., without an interval). More concretely, for example, in examples of  FIGS. 3A  to  3 E, each individual communication period is set so that the next individual communication period Tb starts immediately after the end of the individual communication period Ta. Thereby, efficient communication becomes possible.  
      It is noted that the data processing device  10   a  located at the head of the cascade connection periodically generates the data transmitting signal with a cycle longer than the total of the data processing period Tp and the communication period Tdt, and transmits it. Namely, in order to prescribe the data processing period Tp and the communication period Tdt of the whole robot arm controlling system  100 , the data processing device  10   a  periodically transmits the starting information of the data processing period Tp and also the starting information of the data communication period Tdt. Timing of transmitting the starting information is designed on the basis of an individual timer included in the data processing device  10   a.    
      In the examples of  FIGS. 3A  to  3 E, in the communication period Tdt of the data transmitting signal, the individual communication period is arranged in sequence from the data processing device  10   a  at the upstream position of the cascade connection to the data processing device  10   c  at the downstream position. However, the arrangement is not indispensable. Namely, in the communication period Tdt, if the plural individual communication period is set in an order not to be overlapped with each other on the time axis, the sequence is not necessarily from the data processing device at the upstream position of the cascade connection to the data processing device at the downstream position.  
      In the above embodiment, the description was given of the example that the data collecting system of the present invention was applied to the robot arm control system. However, the application of the present invention is not limited to the robot arm control system. Namely, the present invention can be applied to various systems and circumstances for supplying the output data from the plural data processing devices and data outputting devices to the predetermined devices by the cascade connection.  
      In addition, in the above embodiment, the A/D converting process of the analog output signal from the sensor is illustrated as the example of the data process which is executed in each of the data processing devices. However, the application of the present invention is not limited to that case, and the present invention can be applied to the data processing device which executes various data processes. In the present invention, since the data processing period is set and transmission of the data is inhibited during the period, it is particularly effective to apply the present invention to a data processing device which executes a data process comparatively sensitive to a noise.  
      The invention may be embodied on other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning an range of equivalency of the claims are therefore intended to embraced therein.  
      The entire disclosure of Japanese Patent Application No. 2003-384013 filed on Nov. 13, 2003 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.