Intelligent Motion Systems DSP-402 Homing Mode, Input Data Description, Output Data Description

SECTION 7

Homing Mode

General Information

This chapter describes the method by which a drive seeks the home position (also called, the datum, reference point or zero point). There are various methods of achieving this using limit switches at the ends of travel or a home switch (zero point switch) in mid-travel, most of the methods also use the index (zero) pulse train from an incremental encoder.

control_word

homing_method

homing_speed

Homing

status_word

position_demand_value

Figure 7.1: The Homing Function

Input Data Description

The user can specify the speeds and the method of homing. There are two homing_speeds; in a typical cycle the faster speed is used to find the home switch and the slower speed is used to find the index pulse. The manufacturer is allowed some discre- tion in the use of these speeds as the response to the signals may be Dependent upon the hardware used.

Output Data Description

There is no output data except for those bits in the statusword which return the status or result of the homing process and the demand to the position control loops.

Internal States

There is only one internal state called homing which is reflected in the bits of the statusword.

Controlword (6040h) of Profile Position Mode

15	9	8			7				6	5	4	3	0
See 1.3			Halt	See 1.3						Reserved	Homing Operation Start	See 1.3
MSB													LSB
Bit			Name				Value			Description
							0			Homing Mode Inactive
4		Homing Operation				0			1	Start Homing Mode
			Start				1			Homing Mode Active
						1			0	Interrupt Homing Mode
8			Halt				0			Execute the instruction of bit 4
							1			Stop motion

Table 7.1: Homing Mode Bits of Controlword

Part 2: DSP-402 Implementation 41