CN107807741B - Multi-channel touch sensor based on pointing stick and corresponding control method - Google Patents

Abstract

The invention discloses a multi-channel touch sensor based on a track point, which relates to the field of robot engineering and is realized by integrating a plurality of track points, and comprises a plurality of track points, a mother board connected with the track points and an external wireless transceiver, wherein the track points are connected with the mother board through an eight-pin FPC (flexible printed circuit) card seat with the distance of one millimeter, a main control chip of the mother board selects one track point to be communicated through a sheet multiplexer, the main control chip packs the data according to a preset format and sends the data to an upper computer through a wireless module nRF24L01+, and the upper computer is responsible for subsequent signal processing, wherein the multi-channel touch sensor based on the track points can be connected with eight track points at most, supports sixteen degrees of freedom at most, can control the communication period within one hundred milliseconds, has wide application occasions, and can be used for the design of a multi-degree-of freedom control handle, The design of the gripper at the tail end of the robot and the like.

Description

A multi-channel tactile sensor based on pointing stick and corresponding control method

technical field

The invention relates to a multi-channel tactile sensor, in particular to a multi-channel tactile sensor based on a pointing stick.

Background technique

Tactile sense is one of the important forms for most creatures in nature to obtain information from the external environment. In a broad sense, tactile sense refers to the integration of contact, pressure, sliding, temperature, humidity, etc., while the narrow sense of tactile sense refers to the force sense on the contact surface. The concepts include touch, pressure, and slip. The sense of touch has a very important practical significance for the degree of presence and interactivity in virtual reality technology.

Tactile sensors are sensors used in robotics to mimic tactile functions. Its research began in the 1970s. In the course of more than 40 years of development, researchers at home and abroad have studied the working mechanism of the sensor, the development of sensitive materials, the structural design of the sensor, and the processing of tactile images. A lot of work has been done and great achievements have been made. Tactile sensors can be divided into contact sensors, force-torque sensors, pressure sensors and sliding sensors according to their functions.

At this stage, the challenges of industrial robots mainly focus on interactivity, collaboration and safety. How the robotic arm perceives its surroundings is key to addressing these challenges. Tactile or force sensors are an integral part of the evolution of robots from repetitive work to a certain degree of autonomy. Traditional tactile or force sensors are mostly two-channel or three-channel, but when the robot faces a complex and unstructured environment, this is far from enough. Therefore, it is very necessary to develop a low-cost, highly scalable multi-channel tactile sensor.

U.S. Patent Application No. 5,521,596, titled "Analog input device located in the primary typing area of a keyboard", proposes a mouse control technology that senses the force exerted by fingers Converted to the output of mouse coordinates, its force sensing device is a strain gauge, which can identify the magnitude of the force in two mutually orthogonal directions, but the device has only two channels, namely x and y channels. Although it has been successful in mouse applications, it cannot be applied to the field of industrial robots with higher channel requirements.

Daniel M. Vogt et al. in "IEEE Sensors Journal", 2013, 13(10) published a document "Design and characterization of a soft multi-axis force sensor using embeddedmicrofluidic channels (soft multi-axis force using embedded microfluidic channels) sensor design)”. In this paper, a three-axis soft body force sensor is designed by using the conductive properties of the microfluidic pipeline, and the influence of various design parameters on the sensor effect is also studied. However, this design has shortcomings such as few output channels, small output range, and immature technical application.

U. Kim et al. in "IEEE/ASME Transactions on Mechatronics", 2016, PP(99) published a document "A novel six-axis force/torque sensor for robotic applications (a novel six-axis force/torque sensor for robotic applications) A six-axis force/torque sensor based on capacitance change is designed in "Force/Torque Sensor)". This design has the advantages of compact structure and low cost, but its output range is small, the scalability is poor, and the crosstalk between signal channels is large. And other shortcomings limit its wide range of applications.

Therefore, those skilled in the art are committed to finding a cost-effective solution to build a multi-channel multi-dimensional tactile sensor with simple structure, strong practicability, strong scalability, and low signal channel crosstalk, which can be applied to robots. In this way, high-resolution, highly flexible, and infinitely customizable industrial robots, such as typical force control equipment, can be realized.

SUMMARY OF THE INVENTION

In view of the above existing problems, the present invention designs a multi-channel tactile sensor based on a pointing stick. A multi-channel tactile sensor is realized by a commonly used pointing stick, so as to solve the defects of few tactile sensor channels, poor scalability, and large crosstalk between signal channels in the prior art, and the cost of using the pointing stick is low, which is beneficial to industrial applications, especially can Promote applications on industrial robots. There is no precedent for applying a pointing stick to an industrial robot in this field.

The "pointing stick" mentioned in the present invention refers to a pointing device mainly used in notebook computers at present. The pointing stick was invented by scientist Ted Selker and applied to several laptop brands, including ThinkPad, Dell, HP, and Fujitsu. Different notebook computer manufacturers often have different names for their pointing stick products. ThinkPad calls it "TrackPoint", while Dell calls it "Track Stick", commonly known as "Little Red Dot".

The technical scheme adopted in the present invention is as follows:

The present invention adopts a multi-channel tactile sensor based on a pointing stick, the sensor includes a pointing stick, a connection motherboard and an external wireless transceiver, the pointing stick is electrically connected to the connection motherboard, and the connection motherboard is electrically connected to the connection motherboard. The external wireless transceiver is communicatively connected.

Further, the number of the pointing sticks is 8, and the external wireless transceiver is an nRF24L01+ wireless module.

Further, the pointing stick and the connecting motherboard are connected by an 8-pin FPC card holder with a spacing of 1 mm, the nRF24L01+ wireless module and the on-board wireless transceiver of the connecting motherboard communicate in a 2.4GHz wireless communication mode, and the nRF24L01+ wireless module Can be plugged into a personal computer for data transfer.

Further, the connection motherboard includes a main control chip, two multiplexers, two voltage regulator chips, multiple FPC card holders, onboard wireless transceivers, USB Mini B-type female headers, and resistance-capacitance elements.

Further, the four I/O ports of the main control chip are respectively connected with the chip selection pins OE and channel selection pins S0-S2 of the two multiplexers, and the other two I/O ports of the main control chip are respectively connected to The output pins of the multiplexer are connected to each other; the input pins of the multiplexer are respectively connected with the clock pins and the data pins of the FPC card holder, and the definitions of the pins of the FPC are the same as those of the pointing stick. , the clock pin of the FPC is also connected to the I/O port of the main control chip.

Further, the main control chip is connected with the wireless transceiver module through its own SPI interface, and in addition, the main control chip also allocates an external interrupt port to connect with the interrupt pin of the wireless module.

Further, the corresponding pins of the main control chip are connected with the corresponding pins of the USB Mini B-type female header.

More specifically, the connection motherboard includes an Atmega32u4 main control chip, a model SN74CBT3251 multiplexer, a model SPX1117 voltage regulator chip, an eight-pin FPC card holder with a spacing of one millimeter, a USB Mini B-type female header, and a resistor. Container parts, PF0, PF1, PF4, PF5 of the main control chip are respectively connected with OE, S0, S1 and S2 of the multiplexer SN74CBT3251, PD5 and PD2 of the main control chip are respectively connected with the output leads of the two multiplexers SN74CBT3251. The pins of the first multiplexer SN74CBT3251 are connected to the Dat pins of the 8 FPC card holders respectively, and the B1 to B8 pins of the second multiplexer SN74CBT3251 are respectively connected to the 8 FPC card holders. Also connected to the Clk pin, the mBtn, rBtn and lBtn pins of the 8 FPCs are suspended, the Rst, Dat, and Clk pins are connected to the corresponding resistance-capacitance components according to the impedance requirements, and the Clk pins of the 8 FPCs are respectively and The PC7, PC6, PB6, PB5, PB4, PD7, PD6 and PD4 of the main control chip are connected; the input terminals of the two SPX1117 voltage regulator chips are connected to a 7.4V power supply, and the 3.3V output terminal of the voltage regulator chip supplies power to the wireless module. The 5V output end of the voltage regulator chip supplies power to the entire system, each pin of the connector of the on-board wireless transceiver is connected with the corresponding pin of the SPI interface of the main control chip, and the connection of the on-board wireless transceiver The interrupt request pin of the header is connected to PD0 of the main control chip.

Other components such as resistance-capacitance components and voltage regulator chips are selected and connected according to the requirements of the manual or impedance requirements.

Because the communication between the pointing stick and the connection board can only be completed according to the strict timing sequence, the present invention also provides a method for controlling the multi-channel tactile sensor based on the pointing stick, including the following steps:

Step S1: the main control chip opens a pointing stick channel by controlling the multiplexer, and performs serial communication by controlling the Clk signal of the channel;

Step S2: After opening one of the channels, the main control chip sets a buffer time to wait for the pointing stick to send data;

Step S3: Detect whether data is received within the buffering time, if no data is received, execute step S31; otherwise, execute step S32;

Step S31: forbid the communication of the channel, and assign a value of 0 to the coordinates of the pointing stick, and finally close the channel;

Step S32: the main control chip will delay the communication of the channel after a predetermined time, and at the same time, in order to ensure that the output transmission frequency is fixed, the main control chip will delay another predetermined time;

Step S4: the main control chip will judge whether the number of bytes in the data buffer is three, if so, go to step S41; otherwise, go to step S42;

Step S41: assign the three bytes to corresponding variables and close the channel;

Step S42: assign the relevant variable to zero and clear the buffer, then close the channel, and then copy the relevant variable to the corresponding position of the predefined vector;

Step S5: Repeat the above process until the data of all channels are processed, and then send the vector mentioned above to the upper computer through the wireless module for subsequent processing.

At the same time, the present invention also provides a system implementation comprising the aforementioned pointing stick-based multi-channel tactile sensor.

The present invention can connect up to eight pointing sticks by designing a compact hardware circuit. Since each pointing stick has two degrees of freedom, the present invention supports a maximum of sixteen degrees of freedom; The communication period can be controlled within 100 milliseconds; the wireless data transmission method is adopted, and the data transmission is more convenient and flexible; to sum up, the invention has the characteristics of low cost, strong scalability, flexible configuration, etc., and is widely used in multiple applications. The design of the degree control handle, the design of the robot end gripper, etc.

Description of drawings

Fig. 1 is the system block diagram of the present invention;

Fig. 2 is the hardware principle diagram of the connecting plate of the present invention;

3 is a schematic diagram of data collection and transmission according to a preferred embodiment of the present invention;

FIG. 4 is a graph of sensor signals for eight channels of a preferred embodiment of the present invention.

Detailed ways

The present invention is further described below in conjunction with the accompanying drawings: the present embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following implementations example.

As shown in FIG. 1 , the multi-channel tactile sensor based on the pointing stick according to the present invention includes a pointing stick, a connecting motherboard and an external wireless transceiver module. The module can carry out data transmission, and the external wireless module can be inserted into the USB port of the personal computer so that the upper computer can process and analyze the data. The present invention creatively uses the existing device as a pointing stick to realize a multi-channel tactile sensor, which can be further applied to industrial robots, artificial intelligence and other fields, with low cost, strong expansibility, strong reliability and diversified functions.

As shown in Figure 2, the connection motherboard specifically adopts the model of Atmega32u4 main control chip, the model of SN74CBT3251 multiplexer, the model of SPX1117 series voltage regulator chip, the eight-pin FPC card holder with a spacing of one millimeter, the USB Mini B mother There are several headers, buttons and resistive devices; among them, PF0, PF1, PF4, PF5 of the main control chip are respectively connected with OE, S0, S1 and S2 of the multiplexer SN74CBT3251, and PD5 and PD2 of the main control chip are respectively connected with two more The output pin A of the channel selector SN74CBT3251 is connected. The B1~B8 pins of the multiplexer SN74CBT3251 labeled DATA_SELECT in the figure are connected to the Dat pins of 8 FPC card holders respectively. The multiplexing label labeled CLOCK_SELECT in the figure The B1~B8 pins of the SN74CBT3251 are connected to the Clk pins of the 8 FPC card holders respectively; the mBtn, rBtn and lBtn pins of the 8 FPCs in the figure are floating, and the Rst, Dat and Clk pins are based on the impedance requirements and corresponding resistances. In addition, the Clk pins of the 8 FPCs are connected to PC7, PC6, PB6, PB5, PB4, PD7, PD6 and PD4 of the main control chip respectively; the input terminals of the two voltage regulator chips SPX1117 in the figure are connected to 7.4V power supply, The 3.3V output terminal of the voltage regulator chip supplies power to the wireless module, and the 5V output terminal of the voltage regulator chip supplies power to the entire system; the pins of the wireless module connector in the figure are connected to the corresponding pins of the SPI interface of the main control chip. The interrupt request pin of the module connector is connected to PD0 of the main control chip. The main control chip realizes the PS/2 communication protocol through its own USART interface and the pointing stick.

Figure 3 shows the communication control process between the pointing stick and the connecting motherboard. First, the main control chip should open a pointing stick channel by controlling the multiplexer, and enable serial communication by controlling the Clk signal of the channel; open a channel After that, the main control chip will set a time buffer to wait for the pointing stick to send data.

If no data is received within the buffer time, the communication of the channel is prohibited, and the relevant variables are assigned values at the same time, and finally the channel is closed;

Otherwise, the main control chip will delay for a period of time before prohibiting the communication of the channel. In order to ensure that the output sending frequency is fixed, the main control chip will also delay for a period of time;

Then the main control chip will judge whether the number of bytes in the data register is three. If so, it will assign the three bytes to the corresponding variables and close the channel. Otherwise, the relevant variables will be assigned zero and the register will be cleared, and then close the channel;

Then copy the relevant variables to the corresponding positions of the predefined vectors; repeat the above process until the data of all channels are processed, and then send the previously mentioned vectors to the host computer through the wireless module for subsequent processing.

Figure 4 shows the output information of the eight pointing sticks. During this process, we apply a force for about fifteen seconds to each pointing stick in the order of positive Y, positive X, negative Y, and negative X. ; The signal in the figure can show this process well; in this way, through the reasonable arrangement of the pointing stick and the comprehensive processing of the output signal, the multi-channel tactile sensor based on the pointing stick of the present invention can be widely used.

The preferred embodiments of the present invention have been described in detail above. It should be understood that many modifications and changes can be made according to the concept of the present invention by those skilled in the art without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (9)

1. A method for controlling a track point-based multi-channel touch sensor, the sensor comprising a track point, a connection motherboard and an external wireless transceiver, the track point being electrically connected to the connection motherboard, the connection motherboard being communicatively connected to the external wireless transceiver, the method comprising the steps of:

step S1: the main control chip opens a channel of the pointing stick by controlling the multiplexer and carries out serial communication by controlling the Clk signal of the channel;

step S2: after one channel is opened, the main control chip sets a buffer time to wait for the track point to send data;

step S3: detecting whether data are received or not in the buffering time, if the data are not received, executing the step S31, otherwise, executing the step S32;

step S31: forbidding the communication of the channel, assigning the coordinate of the pointing stick as 0, and finally closing the channel;

step S32: the main control chip delays for a preset time and then forbids the communication of the channel, and simultaneously, in order to ensure that the output sending frequency is fixed, the main control chip delays for another preset time;

step S4: the main control chip judges whether the number of bytes in the data buffer is three, if yes, the step S41 is executed, otherwise, the step S42 is executed;

step S41: assigning the three bytes to corresponding variables respectively and closing the channel;

step S42: assigning the relevant variable to zero and emptying a buffer, then closing the channel, and copying the relevant variable to a corresponding position of a predefined vector;

step S5: and repeating the processes of the steps S1-S4 until the data of all channels are processed, and then sending the vector mentioned earlier to the upper computer through the wireless module for subsequent processing.

2. The method of controlling a track point-based multi-channel tactile sensor of claim 1, wherein the number of track points is 8 and the external wireless transceiver is an nRF24L01+ wireless module.

3. The method for controlling a track point-based multi-channel tactile sensor according to claim 1, wherein the track point and the connection motherboard are connected through an 8-pin FPC card socket with a 1 mm pitch, and the nRF24L01+ wireless module and the connection motherboard on-board wireless transceiver communicate in a 2.4GHz wireless communication manner, and the nRF24L01+ wireless module can be inserted into a personal computer for data transmission.

4. The method of controlling a track point-based multi-channel tactile sensor of claim 1, wherein the connection motherboard comprises a master control chip, two multiplexers, two voltage stabilization chips, a plurality of FPC holders and an on-board wireless transceiver, a USB MiniB type female head, and a resistive-capacitive element.

5. The method for controlling a multi-channel tactile sensor based on a pointing stick according to claim 4, wherein 4I/O ports of the main control chip are respectively connected to chip select pins OE and channel select pins S0-S2 of two multi-channel selectors, and the other 2I/O ports of the main control chip are respectively connected to output pins of the multi-channel selectors; the input pins of the multiplexer are respectively connected with the clock pin and the data pin of the FPC card seat, the definition of each pin of the FPC is the same as that of the pin of the pointing stick, and the clock pin of the FPC is also connected with the I/O port of the main control chip.

6. The method for controlling a multi-channel track point-based tactile sensor according to claim 4, wherein the main control chip is connected to the wireless transceiver module through its own SPI interface, and further the main control chip is assigned an external internal break to be connected to an interrupt pin of the wireless module.

7. The method of controlling a track point-based multi-channel tactile sensor of claim 4, wherein corresponding pins of the main control chip are connected with corresponding pins of a USB Mini B-type female header.

8. The method of claim 4, wherein the connection mother board includes an Atmega32u4 master chip, a model SN74CBT3251 multiplexer, a model SPX1117 ballast chip, eight-pin FPC card holders with a one-mm pitch, a USB Mini B type female header, and a capacitance blocking device, wherein PF0, PF1, PF4, and PF5 of the master chip are connected to OE, S0, S1, and S2 of the multiplexer SN74CBT3251, respectively, PD5 and PD2 of the master chip are connected to output pins of two multiplexers SN74CBT3251, respectively, B1-B8 pins of a first multiplexer SN74CBT3251 are connected to Dat pins of 8 FPC cards, respectively, B1-B8 pins of a second multiplexer SN74CBT3251 are connected to Clk 3256 pins of 8 FPC card holders,

the pins of mBtn, rBtn and lBtn of the 8 FPCs are suspended, the pins of Rst, Dat and Clk are connected with corresponding resistance-capacitance elements according to impedance requirements, and the pins of the 8 FPCs are respectively connected with PC7, PC6, PB6, PB5, PB4, PD7, PD6 and PD4 of the main control chip; the input termination 7.4V power of two SPX1117 voltage stabilizing chip, wireless module power supply is given to voltage stabilizing chip 3.3V's output, whole system power supply is given to voltage stabilizing chip's 5V output, each pin of board-mounted wireless transceiver's connector is connected with the corresponding pin of main control chip SPI interface, the interrupt request pin of board-mounted wireless transceiver's connector and main control chip's PD0 link to each other.

9. A robot implementing the method of controlling a track point-based multi-channel tactile sensor of any of claims 1-8.

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