Based CANI bus electric truck control handle design

 

(Harbin Institute of Technology Control Science and Engineering, Harbin 150001)

 

    Abstract: Currently, most electric truck each control signal transmission signal line is used alone, harness complex and low reliability. To address this shortcoming, this paper uses built-in CAN controller AT90CAN128 microcontroller as the processor, is designed based on CAN bus control handle. The handle has a conveyance speed, the lift characteristics of the goods buffer deceleration, and increased snail line, emergency reverse safe driving truck and other support functions. Paper, according to these features and characteristics of the composition of the CAN bus, to develop the appropriate communication protocol, and the entire control handle hardware and software design are described in detail j experiments show that the CAN bus control handle has a simple harness, security, reliability advantages.

 

    Keywords: electric truck; control handle; CAN bus: AT90CAN128

 

    CLC: TP336 Document code: A

 

    CAN-Controller Area Network is an effective support for distributed control or real-time control of the serial communications network. CAN bus was first to solve many modern vehicle control and data exchange between the test equipment and the development of a serial data communication protocol, which is a multi-master bus, the communication medium can be twisted pair, coaxial cable , fiber optics, communication speed up lMb / s. CAN bus communication interface integrated CAN protocol physical layer, data link layer functions can be paired Gazette communication data frame processing, including bit-stuffing, block coding, cyclic redundancy check, discrimination and other work priorities.

 

    Truck loading and unloading of cargo in containers and other process has played a very important role, the previous truck no engine engine relies entirely on human promotion, labor intensive and inefficient, there is now a large number of electric truck, saving a lot of labor costs, but the current function of the control handle on the market signals are transmitted via the respective signal line, and poor reliability. CAN bus technology has been widely in automotive electronics applications with high reliability. This article will CAN bus technology to electric transportation vehicles, presents a high security, high reliability design methods. This design will all control signals transmitted via the CAN bus and the CAN test card test control signal data, connecting the motor controller tuning, and have achieved very good results, in order to create a practical basis for industrial production.

 

A hardware design

 

1.1 AT90CAN128 special ilt Overview

 

    AT90CAN128 is based on the AVR RISC architecture 8-bit high-performance, low-power CMOS microprocessor. It uses an advanced instruction set and single-cycle instruction execution time, the data throughput of up to 1MIPS/MHz, its core combines a rich instruction set with 32 general purpose working registers. All registers are directly connected to the ALU. By combining an 8-bit RISC CPU with In-System Programmable Flash on a monolithic chip, to many embedded control applications, providing a flexible and cost effective solution.

 

    AT90CAN128 built-in 10-bit resolution successive approximation type AD converter module. ADC with an 8-channel analog multiplexer connections, the port of F from 8 single-ended voltage inputs. Single-ended voltage input to OV (GND) as the reference. ADC includes a sample and hold circuit to ensure that the conversion process to the ADC input voltage is kept constant. Nonlinearity with 0.5LSB, +2 LSB Absolute Accuracy, 13 ~ 260ys conversion time, the highest resolution sampling rates up to 15kb / s.

 

    Within AT90CAN128 amount in full compliance CAN2.OA and 2.OB standard protocol of the CAN controller. Using MOb (Message Object) method for data transmission and reception, a total of 15 MOb, increased from 0 to 14. Each MOb have their own separate identifier and mask, 8-bit data buffer, 11-bit identifier (2.OA agreement), but also expandable to 29 (2.OB agreement), there are send, receive, as well as auto-reply frame buffer receive mode, the maximum transfer rate of up to 8MHz lMb / s. A MOb a CAN message frame processing all the information. Each MOb have been placed in a page (CANPAGE) in to save MOb page number is the serial number.

 

1.2 Functional design control handle

 

    This design of electric truck control handle to achieve the van forward and back, cargo lift landing, after the shift fork forward cargo handling and other basic functions, also has a snail line, horn, emergency and other support truck safety reverse driving function.

 

    Truck forward and back on the ground is the normal driving functions: lifting cargo refers to cargo lift landing function: forward backward forks is lifted to the right of the goods when the goods are sent forward position of the function : Speaker is in the process of moving forward is used to alert personnel Note: snail line refers to the van in the fast moving obstacles encountered during deceleration when an emergency situation requires a constant slow speed: Emergency reverse is the van obstacles encountered in the process of moving the reverse need emergency stop buffer function. Emergency reverse is controlled by a key switch real view, when the encounter obstacles, due to inertia will top this switch in the operator's abdomen to protect the driving safety, also known as belly switch.

 

1.3 Control handle hardware circuit

 

    Forward and back, lifting landed, after the shift forward analog input generated by the linear Hall element SS495A, snail line, speakers, emergency reverse the digital signals generated by the key switch, the signal input to the processor for processing AT90CAN128 and designed in accordance with the CAN bus communication protocol communicate with the motor controller to drive the corresponding motor.

 

    Vans and fork forward and back after the forward shift of the analog input, while the lift landing selectable as analog input or a digital input. This design can make with a control handle can be applied to different types of truck simulator parts cost savings, such as pallet trucks are only about 120mm lift height, generally with digital inputs, Stacker lifting about 3 ~ 5m height, to reduce its carrying heavy cushioning when landing requires the use of the analog input. Differential voltage of the Hall element and a Hall element and the magnet substantially to the distance between the linear relationship and the signal input to the AD converter module AT90CAN128 differential and linear processing.

 

1.4 communications protocol developed

 

According to the previous section of the transport vehicle designed to function in signal communication protocols defined role of each byte, as shown in Table 1.

 

Table for digital input signals: one indicates key has been pressed; 0 means the button is not pressed. For analog input signal: Positive values ​​indicate forward, lifting, forward; negative value indicates reverse; 0 means stop. Bit6, Bit7 Hall linear and switching can access, a digital signal will be given based on the threshold defined within the ON / OFF changes between.

 

2 Software Design

 

2.1 Input Signal detection process

 

    Taking into account the mechanical installation errors, in order to make the linear Hall element mechanical and electrical 0:00 0:00 coincide in program design, each time power is automatically search for 0:00, and 0:00 to set up a basis of this dead zone, in order to Cancel fluctuate around zero.

 

    The signal processing in the analog input after the general linear output, according to the actual experimental results, if the lifting of heavy objects larger mass, while landing will have a greater impact, requiring the landing of the initial time there is a slow buffer, the corresponding need to be landed analog input signal at the output changes when changes to the preceding slower exponential curve output.

 

    Lifting landed input signal can be analog or digital jumper amount of choice, the digital inputs can be key forms, may also open Fujia linear Hall to set a threshold, relatively simple. Below to select the analog input, for example, describes the system after power signal loop detection processing program flow, the flow chart shown in Figure 3.

 

2.2 CAN controller initialization

 

    Before initializing the CAN General Control register is set to the highest position a reset mode. The main initial work including loading identifier and mask, set the baud rate. Finished, return to operation mode is cleared. Message identifier is defined as OxlEO, using CAN2.OA protocol standard frame transmission, the baud rate is 125kb / s, the transmission interval period is 15ms. The following shows the CAN controller initialization procedure: 2.3 CAN messages

 

    Send a message sent using direct ways. First, by setting registers to specify CANPAGE be sent MOb, loading data into CANMSG register, and then by the CANCDMOB register to control transmission operation, the message is sent, waiting to be sent after the success of the Qing sent successfully flag. The transmission module to 15ms timer interrupt can be sent periodically, in order to achieve the control function of the handle, and then by the motor controller drives the corresponding motor. Sending program is given below:

 

3 Conclusion

 

    Comparison with other types of microcontrollers comparison, AT90CAN128 in the design of data collection has its obvious advantages, especially in built-in CAN controller, reducing equipment costs, simplifying the hardware structure, improve communication efficiency, security, and reliability sex. Software design through on MOb configuration settings to achieve the message queue, this method is more flexible and convenient.

 

    The control handle increased snail line, emergency reverse feature, making truck run more safely and efficiently. Cargo lift landing exponential curve cushion design reduces damage to the goods, as well as the goods right fork and other components for damage to a minimum, extending the life of truck. The handle through the CAN bus with Zapi Spa production COMBI AC1 motor controller connected Experiments show that the design of CAN bus control handle running well, can achieve the desired functionality.